@article { ISI:000254648100007, title = {In situ synthesis of Pt nanoparticles in SBA-15 by encapsulating in modified template micelles: size restricted growth within the mesochannels}, journal = {Journal of Materials Chemistry}, volume = {18}, number = {15}, year = {2008}, month = {FEB}, pages = {1765-1770}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A truly in situ and simple method is developed for nanoparticle incorporation within the mesochannels of SBA-15 involving dispersion of metal precursors in surfactant-modified polymer micelles. The diffusion of the precursor within the micellar structure is aided by interaction with the cationic head group of the surfactant leading to a unique method to facilitate the formation of highly disperse, uniform nanoparticles molded by the walls of the mesochannels. The nanoparticle incorporated mesoporous material has a highly enhanced surface area and adsorption capabilities in comparison to its parent materials without any pore blockage which makes this method ideal for the preparation of nanocatalysts.

}, issn = {0959-9428}, doi = {10.1039/b717991j}, author = {Prashar, Atul K. and Hodgkins, Robert P. and Kumar, Rajiv and Devi, R. Nandini} } @article { ISI:000274929000006, title = {In situ encapsulation of pt nanoarchitectures of varying morphologies in mesoporous compounds}, journal = {Chemistry of Materials}, volume = {22}, number = {5}, year = {2010}, month = {MAR}, pages = {1633-1639}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nanoparticle morphology could be engineered and fine-tuned based on a novel in situ template method Different shapes of platinum nanoparticles were obtained from very low concentrations of precursors and could be isolated exclusively inside the mesochannels of SBA-15 This was achieved by dispersing a platinum precursor in surfactant modified polymer to different extents and using these composite materials as templates for the formation of mesoporous silica [PtCl(6)](2-) interacts with the cationic headgroup of the surfactant and facilitates the isolation of precursors within the composite template leading to the formation of nanoparticles molded by the walls of the mesochannels when calcined When this [PtCl(6)](2-)-surfactant-polymer micelle composite is aged for different duration, Pt nanoparticles of various morphologies like spheroids, nano rugby balls, and nanorods are obtained

}, issn = {0897-4756}, doi = {10.1021/cm9036499}, author = {Prashar, Atul K. and Hodgkins, Robert P. and Chandran, Jima N. and Rajamohanan, P. R. and Devi, R. Nandini} } @article { ISI:000295149400011, title = {In situ encapsulation of Pt nanoparticles in mesoporous silica: synthesis, characterisation and effect of particle size on CO oxidation}, journal = {Applied Catalysis A-General}, volume = {403}, number = {1-2}, year = {2011}, month = {AUG}, pages = {91-97}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Pt nanoparticles of narrow size distribution and average particle size of 4.4 nm are isolated exclusively inside SBA-12 mesoporous silica by a novel in situ method. The interaction of Pt precursor with surfactant-polymer composite micelle is followed by NMR and UV studies. The final Pt incorporated silica material is characterised by XRD, TEM and N(2) adsorption. The mesoporous nature of the silica is found to be intact after Pt incorporation without any pore blockage. CO oxidation activity of this material is compared with that of mesoporous silica incorporating different sizes of Pt viz., 1.8, 3.6 and 8 nm. Activation energies of CO oxidation for all these materials are calculated by a simple differential method based on first principles. A comparison of activation energies and single site yields reveals that these parameters are distinguishably less in catalyst containing 1.8 nm Pt nanoparticles but more or less same in catalysts containing 3.6, 4.4 and 8 nm Pt nanoparticles. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {CO oxidation, In situ synthesis, Mesoporous silica, Pt nanoparticle}, issn = {0926-860X}, doi = {10.1016/j.apcata.2011.06.016}, author = {Prashar, Atul K. and Mayadevi, S. and Rajamohanan, P. R. and Devi, R. Nandini} } @article { ISI:000306674200026, title = {Disordered brownmillerite Ba2InCeO5+delta with enhanced oxygen reduction activity}, journal = {Chemistry of Materials}, volume = {24}, number = {14}, year = {2012}, month = {JUL}, pages = {2823-2828}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A disordered brownmillerite, Ba2InCeO5+delta, with slight tetragonal distortion from ideal cubic perovskite is synthesized and its oxygen reduction reactivity tested. The material displayed oxygen reduction behavior in alkaline solution comparable to that of standard 40 wt \% Pt/C catalyst and attractive activity characteristics which renders it a potential system for low temperature fuel cell applications.

}, keywords = {brownmillerite, fuel cell, oxygen reduction reaction, Rietveld refinement}, issn = {0897-4756}, doi = {10.1021/cm301863x}, author = {Jijil, Chamundi P. and Unni, SreeKuttan M. and Sreekumar, Kurungot and Devi, R. Nandini} } @article { ISI:000311180800010, title = {Effect of particle size on selective hydrogenation of cinnamaldehyde by Pt encapsulated in mesoporous silica}, journal = {Catalysis Communications}, volume = {28}, year = {2012}, month = {NOV}, pages = {42-46}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Pt nanoparticles of various sizes, viz. 8. 4.9, 3.6 and 1.8 nm were encapsulated in 2D hexagonal mesoporous silica by in-situ synthesis as well as post synthetic modifications so that the final catalyst composition was \<= 1 wt.\% Pt/SiO2. A kinetic analysis of the effect of particle size on selective hydrogenation of cinnamaldehyde was carried out on these catalysts. It was found that the materials, even at such low loading of Pt, were very active for the hydrogenation and selective for the desired product, cinnamyl alcohol. Among the different particle sizes, selectivity was found to be the highest on 8 nm particles. Kinetic analysis shows that the reaction follows a consecutive reaction pathway. (C) 2012 Elsevier B.V. All rights reserved.

}, keywords = {alpha, beta-Unsaturated aldehydes, Cinnamaldehyde hydrogenation, Kinetic analysis, Mesoporous silica, Pt nanoparticles, Selective hydrogenation}, issn = {1566-7367}, doi = {10.1016/j.catcom.2012.08.017}, author = {Prashar, Atul K. and Mayadevi, S. and Devi, R. Nandini} } @article { ISI:000303426500018, title = {Evidence of cationic Pt active for water-gas shift reaction: Pt-doped BaCeO3 perovskite}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {17}, year = {2012}, month = {MAY}, pages = {9526-9532}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Precious metal incorporated into stable lattices like perovskites can be envisaged as an alternative catalysts to address deactivation problems. Here we report the barium cerate perovskite doped with varying amounts of Pt as catalysts for the water-gas shift reaction whereby ionic Pt is evidenced to be active. It is found that maximum CO conversion occurs above 325 degrees C and increases more than 2-fold after the first cycle. XPS analysis shows that after the first cycle, more ionic Pt species are present on the surface of the catalyst. X-ray and neutron diffraction studies also indicate the presence of oxygen vacancies that increases with increasing Pt substitution.

}, issn = {1932-7447}, doi = {10.1021/jp212211d}, author = {Rajesh, Thattarathody and Rajarajan, Anakot K. and Gopinath, Chinnakonda S. and Devi, R. Nandini} } @article { ISI:000302893400028, title = {In situ encapsulation of ultra small ceria nanoparticles stable at high temperatures in the channels of mesoporous silica}, journal = {Microporous and Mesoporous Materials}, volume = {155}, year = {2012}, month = {JUN}, pages = {215-219}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Ultra small ceria nanoparticles of sizes \<2 nm stable at 500 degrees C are encapsulated in the channels of mesoporous silica by employing a novel method of synthesis. The method involves modifying non-ionic polymer templates with ionic surfactants to enhance anchoring of metal ion precursors. In this way, further silica wall formation around the template ensures isolation of the nanoparticles exclusively within the channels after template removal by heat treatment. Further understanding of the interaction of the composite template system and cerium precursor is gained by cyclic voltammetric studies. (C) 2012 Elsevier Inc. All rights reserved.

}, keywords = {ceria, Encapsulation, Mesoporous silica, Template synthesis}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2012.02.006}, author = {Ghosh, Sumona and Jijil, Chamundi P. and Devi, R. Nandini} } @proceedings { ISI:000306973500619, title = {Noble metal ions incorporated in lattice points of perovskites - water gas shift activity of BaCe1-xPtxO3-d}, volume = {1447}, year = {2012}, note = {56th DAE-Solid State Physics Symposium (SSPS), SRM Univ, Kattankulathur, INDIA, DEC 19-23, 2011}, month = {JUN}, pages = {1277-1278}, publisher = {Govt India, Dept Atom Energy (DAE), Board Res Nucl Sci (BRNS)}, address = {2 Huntington Quadrangle, Ste 1no1, Melville, NY 11747-4501 USA}, abstract = {

Recently precious metals supported on oxides were reported to be very promising catalysts for the lower-temperature WGS reaction. Here we report the synthesis of platinum doped barium cerate and its use as catalysts for WGS reaction. It has been found that maximum CO conversion was obtained at 350 degrees C which enhanced after the first cycle. XPS analysis shows that after the first cycle more ionic Platinum species are present on the surface of the catalyst. Neutron diffraction at room temperature shows that the oxygen vacancies are in the O2 position and increases with increasing Pt substitution.

}, keywords = {BaCeO3, Neutron diffraction, Platinum catalysis, WGS reaction}, isbn = {978-0-7354-1044-2}, issn = {0094-243X}, doi = {10.1063/1.4710478}, author = {Jijil, Chamundi P. and Rajarajan, A. K. and Devi, R. Nandini}, editor = {Mittal, R. and Chauhan, A. K. and Mukhopadhyay, R.} } @article { ISI:000311971400028, title = {Novel porous silica encapsulated Au nanoreactors as peroxidase mimic for one-pot glucose detection}, journal = {New Journal of Chemistry}, volume = {36}, number = {12}, year = {2012}, month = {DEC}, pages = {2625-2629}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The peroxidase family of natural enzymes facilitate H2O2 reduction by one electron transfer through aromatic substrates, if chromogenic, they can be used in the colorimetric detection of H2O2 and subsequently glucose in tandem with glucose oxidase. Au nanoparticles encapsulated within porous silica exhibited peroxidase mimetic activity and kinetic parameter evaluation indicates an excellent affinity for H2O2. It is also shown to have a detection capability for glucose in very low concentrations and could be used for glucose detection in a one-pot assay. The material is synthesised by using cation-ended thiol-stabilised ultra small gold clusters as precursors. Removal of the thiols creates micropores within the silica, making this material unique in that the active centres are protected inside the silica, yet are accessible to reactant molecules. This characteristic makes the material ideal as a detection tool where attrition resistance will be advantageous.

}, issn = {1144-0546}, doi = {10.1039/c2nj40665a}, author = {Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article { ISI:000306215900061, title = {Structure engineering of naphthalene diimides for improved charge carrier mobility: self-assembly by hydrogen bonding, good or bad?}, journal = {Journal of Materials Chemistry}, volume = {22}, number = {30}, year = {2012}, month = {MAY}, pages = {15235-15246}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Two families of naphthalene diimide (NDI) derivatives were compared and contrasted for the effect of self-assembly on charge carrier transport. One series of NDI derivatives had a terminal phenyl ring attached to a hexyl spacer substituted naphthalene core either through an ester or an amide linkage (NDI-E and NDI-A, respectively), while the other series had a 3,4,5-tridodecyloxy phenyl unit (NDI-E3, NDI-A3) instead of the terminal phenyl unit. Solution processed thin films of these molecules exhibited n-type charge transport characteristics in a bottom gate top contact organic field effect transistor (OFET) geometry. The amide derivatives showed evidence of self-organization with observation of red shifted aggregate emission in solution as well as solid state. Variable temperature FTIR studies in the solid state confirmed the existence of strong hydrogen bonding which could be broken only at very high temperature. However, contrary to expectations, the NDI ester derivatives showed better device efficiency with electron mobilities in the range 8.5 x 10(-3) to 2 x 10(-2) cm(2) V-1 s(-1) and on/off ratio similar to 10(4). The thin film crystallinity and morphology of NDI-E and NDI-A were examined through X-ray diffraction and atomic force microscopy (AFM). The correlation of crystallinity, hydrogen bonding and charge carrier mobility was studied using energy minimized structures from density functional theory (DFT). The higher electron mobility of ester linked NDI derivatives over the amide linked ones was attributed to the freedom in charge transport pathways offered by a three dimensional crystalline organization in the ester compared to the restricted directional hydrogen bonding interaction in the amide derivatives.

}, issn = {0959-9428}, doi = {10.1039/c2jm32554c}, author = {Kolhe, Nagesh B. and Devi, R. Nandini and Senanayak, Satyaprasad P. and Jancy, B. and Narayan, K. S. and Asha, S. K.} } @article { ISI:000299584800014, title = {Ultrasmall gold cluster arrays encapsulated in silica nanospheres: applications in fluorescence imaging and catalysis}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {2}, year = {2012}, month = {JAN}, pages = {1748-1754}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Facile synthesis of ultrasmall gold nanoclusters of size \<2 nm dispersible in water using a novel quaternary ammonium ligand is reported. Further, arrays of these nanoclusters are encapsulated in monodisperse silica nanospheres of size 25-30 nm. The photophysical characteristics of the clusters are found to be intact upon encapsulation, rendering the resulting composite material ideal for fluorescence imaging applications. We have further shown the utilization of these materials in catalysis as precursors for Au nanopartides encapsulated in porous silica.

}, issn = {1932-7447}, doi = {10.1021/jp2093737}, author = {Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article { ISI:000320929200041, title = {Pd ultra-small clusters as precursors for silica-encapsulated Pd nanoreactors: highly sinter-resistant catalysts}, journal = {Chemcatchem}, volume = {5}, number = {7}, year = {2013}, month = {JUL}, pages = {1911-1916}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Sintering and consequent deactivation in supported metal catalysts is a severe problem encountered in heterogeneous catalysis. This problem can be addressed by encapsulating active metal nanoparticles within inert oxides such as silica, provided the oxide shell is porous to enable access of reactant molecules to the nanoparticle surface to facilitate catalysis. We report the synthesis of highly sinter-resistant silica-encapsulated Pd catalysts with nanoparticle sizes stabilized at (3.4 +/- 0.6)nm at high temperatures of approximately 750 degrees C. The synthesis was achieved by utilizing thiol-protected ultra-small clusters of Pd as precursors for silica encapsulation. The ultra-small clusters were synthesized by using propyl ammonium functionalised thiols making them water-dispersible and amenable for silica encapsulation. Abundance of organics also aided in creating porosity subsequent to calcination at high temperatures.

}, keywords = {cluster compounds, Encapsulation, nanoreactors, Palladium, silicates}, issn = {1867-3880}, doi = {10.1002/cctc.201200908}, author = {Samanta, Anupam and Devi, R. Nandini} } @article { ISI:000329137400042, title = {Selective imaging of quorum sensing receptors in bacteria using fluorescent Au nanocluster probes surface functionalized with signal molecules}, journal = {ACS Applied Materials \& Interfaces}, volume = {5}, number = {24}, year = {2013}, month = {DEC}, pages = {13076-13081}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Fluorescent ultrasmall gold clusters decorated with bacterial quorum sensing signal molecules, acyl homoserine lactone, are synthesized. These fluorescent probes are found to have emission in the near-infrared spectral region advantageous for bioimaging. Imaging studies using different. strains of bacteria with and without acyl homoserine lactone receptors with the aid of confocal microscopy have shown that the probe interacts preferentially with cells possessing these receptors. This indicates that, with appropriate surface functionalization, the Au clusters can be used for receptor specific detection with enhanced selectivity.

}, keywords = {Au nanoclusters, Biosensor, fluorescence imaging, quorum sensing}, issn = {1944-8244}, doi = {10.1021/am404093m}, author = {Mukherji, Ruchira and Samanta, Anupam and Illathvalappil, Rajith and Chowdhury, Somak and Prabhune, Asmita and Devi, R. Nandini} } @article { ISI:000332388900042, title = {Confined space synthesis of fully alloyed and sinter-resistant AuPd nanoparticles encapsulated in porous silica}, journal = {Journal of Materials Chemistry A}, volume = {2}, number = {12}, year = {2014}, month = {JAN}, pages = {4398-4405}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Facile synthesis of highly sinter-resistant silica encapsulated Au-Pd alloy nanocatalysts with average particle size stabilized at similar to 4.5 nm even after calcination at 750 degrees C temperature is reported. The synthesis was achieved by utilizing thiol protected ultra small clusters of Au and Pd as precursors for silica encapsulation. The presence of intimate mixtures of the clusters within silica encapsulation ensures the formation of fully alloyed nanoparticles at high temperatures, at the same time controlling further growth and sintering. At optimum alloy compositions, these catalysts showed high catalytic activity for CO oxidation displaying low light-off temperatures.

}, issn = {2050-7488}, doi = {10.1039/c3ta15194h}, author = {Samanta, Anupam and Rajesh, Thattarathody and Devi, R. Nandini} } @article { ISI:000347498500064, title = {Effect of pt incorporation in LaBO3 (B = Mn, Fe, Co) perovskites on water gas shift activity}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {395}, year = {2014}, month = {DEC}, pages = {506-513}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Pt incorporated perovskites LaBO3 (B = Mn, Co, Fe) were synthesised and characterised to understand the charge state of Pt in these materials. At the temperature range used in this study, Pt could be stabilised in ionic form in Co and Fe perovskites but not in LaMnO3. Consequent to incorporation of Pt in +2 and +4 oxidation states, reduction in B site ion charge state occurred, enhancing oxygen vacancies. Pt doped Co and Fe perovskites showed high activity for CO conversion under water gas shift conditions but the activity characteristics were found to be different for the two catalysts; LaCo1-xPtxO3-delta showed methanation whereas the Fe counterpart was active in water gas shift reaction. It was also observed that methanation could be decreased and water gas shift enhanced in case of Pt doped Co perovskite when compared to Pt impregnated perovskite or mixed oxides. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Methanation, Perovskites, Pt doping, Water gas shift reaction, XANES}, issn = {1381-1169}, doi = {10.1016/j.molcata.2014.09.015}, author = {Rajesh, Thattarathody and Upadhyay, Anuj and Sinha, Anil K. and Deb, Sudip K. and Devi, R. Nandini} } @article { ISI:000328952500024, title = {Investigations into variations in local cationic environment in layered oxide series InGaO3(ZnO)(m) (m=1-4)}, journal = {Dalton Transactions}, volume = {43}, number = {5}, year = {2014}, month = {NOV}, pages = {2120-2126}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Layered oxides of the series InGaO3(ZnO)(m) (m = 1-4) are interesting due to their structural anisotropy. Here, we report a comprehensive study of their structural details, focusing on the local cationic environment in bulk powder samples by MASNMR and EXAFS, which is hitherto not attempted. It is found that the Ga geometry varies gradually from pure pentacoordinated to a mixture of penta and tetracoordinated with increasing amounts of tetracoordination as we move across the series, contrary to previous reports suggesting exclusively trigonal bipyramidal coordination in all the compounds. A similar observation is also made in the case of Zn and structural evolution involving the dissolution of Ga in a ZnO4 tetrahedral network in a sandwich layer can be discerned, as the insulating ZnO layer size increases.

}, issn = {1477-9226}, doi = {10.1039/c3dt52011k}, author = {Narendranath, Soumya B. and Yadav, Ashok Kumar and Ajithkumar, Thalasseril G. and Bhattacharyya, Dibyendu and Jha, Shambhu Nath and Dey, Krishna K. and Raja, Thirumalaiswamy and Devi, R. Nandini} } @article { ISI:000344978200129, title = {Nanostructured donor-acceptor self assembly with improved photoconductivity}, journal = {ACS Applied Materials \& Interfaces}, volume = {6}, number = {21}, year = {2014}, month = {NOV}, pages = {19434-19448}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nanostructured supramolecular donor-acceptor assemblies were formed when an unsymmetrical N-substituted pyridine functionalized perylenebisimide (UPBI-Py) was complexed with oligo(p-phenylenevinylene) (OPVM-OH) complementarily functionalized with hydroxyl unit and polymerizable methacrylamide unit at the two termini. The resulting supramolecular complex [UPBI-Py (OPVM-OH)](1.0) upon polymerization by irradiation in the presence of photoinitiator formed well-defined supramolecular polymeric nanostructures. Self-assembly studies using fluorescence emission from thin film samples showed that subtle structural changes occurred on the OPV donor moiety following polymerization. The 1:1 supramolecular complex showed red-shifted aggregate emission from both OPV (similar to 500 nm) and PBI (similar to 640 nm) units, whereas the OPV aggregate emission was replaced by intense monomeric emission (similar to 430 nrn) upon polymerizing the methacrylamide units on the OPVM-OH. The bulk structure was studied using wide-angle X-ray diffraction (WXRD). Complex formation resulted in distinct changes in the cell parameters of OPVM-OH. In contrast, a physical mixture of 1 mol each of OPVM-OH and UPBI-Py prepared by mixing the powdered solid samples together showed only a combination of reflections from both parent molecules. Thin film morphology of the 1:1 molecular complex as well as the supramolecular polymer complex showed uniform lamellar structures in the domain range \<10 rim. The donor-acceptor supramolecular complex [UPBI-Py (OPVM-OH)](1.0) exhibited space charge limited current (SCLC) with a bulk mobility estimate of an order of magnitude higher accompanied by a higher photoconductivity yield compared to the pristine UPBI-Py. This is a very versatile method to obtain spatially defined organization of n and p-type semiconductor materials based on suitably functionalized donor and acceptor molecules resulting in improved photocurrent response using self-assembly.

}, keywords = {donor-acceptor, hydrogen bonding, oligo(p-phenylenevinylene), Perylenebisimide, photoconductivity, supramolecular polymeric nanostructures}, issn = {1944-8244}, doi = {10.1021/am5055542}, author = {Saibal, B. and Ashar, A. Z. and Devi, R. Nandini and Narayan, K. S. and Asha, S. K.} } @article { ISI:000344997500118, title = {Nitrogen-doped graphene interpenetrated 3D Ni-nanocages: efficient and stable water-to-dioxygen electrocatalysts}, journal = {Nanoscale}, volume = {6}, number = {21}, year = {2014}, month = {SEP}, pages = {13179-13187}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Herein, we report the synthesis of a nitrogen-doped graphene (NGr) interpenetrated 3D Ni-nanocage (Ni-NGr) electrocatalyst by a simple water-in-oil (w/o) emulsion technique for oxidation of water to dioxygen. Correlation of adsorption of NGr and subsequent interpenetration through the specific surface plane of nickel particles as well as the concomitant interaction of N and C with Ni in the nano-regime has been investigated. Apart from the benefits of the synergistic interactions between Ni, N, and C, the overall integrity of the structure and its intra-molecular connectivity within the framework help in achieving better oxygen evolution characteristics at a significantly reduced overpotential. The engineered Ni-NGr nanocage displays a substantially low overpotential of similar to 290 mV at a practical current density of 20 mA cm(-2) in 0.1 M KOH. In comparison, NGr and Ni-particles as separate entities give overpotentials of similar to 570 and similar to 370 mV under similar conditions. Moreover, the long term stability of Ni-NGr was investigated by anodic potential cycling for 500 cycles and an 8.5\% increment in the overpotential at 20 mA cm(-2) was observed. Additionally, a chronoamperometric test was performed for 15 h at 20 mA cm(-2), which highlights the better sustainability of Ni-NGr under the actual operating conditions. Finally, the quantitative estimation of evolved oxygen was monitored by gas chromatography and was found to be 70 mmol h(-1) g(-1) of oxygen, which is constant in the second cycle as well.

}, issn = {2040-3364}, doi = {10.1039/c4nr03578j}, author = {Dhavale, Vishal M. and Gaikwad, Sachin S. and George, Leena and Devi, R. Nandini and Kurungot, Sreekumar} } @article { ISI:000340446300061, title = {Photocatalytic H-2 evolution from water-methanol system by anisotropic InFeO3(ZnO)(m) oxides without cocatalyst in visible light}, journal = {ACS Applied Materials \& Interfaces}, volume = {6}, number = {15}, year = {2014}, month = {AUG}, pages = {12321-12327}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

InFeO3(ZnO)(m), series of oxides are found to give unprecedented H-2 evolution from water-methanol mixtures without using any cocatalysts. This family of compounds has an anisotropically layered structure in which Zn/FeOn polyhedra are sandwiched between InO6 octahedral layers. Local structure characterization by X-ray absorption spectroscopy reveals that Zn coordination changes from pentacoordinated to tetrahedral geometry across the series, whereas Fe geometry remains trigonal bipyramidal in all the compounds. This peculiar structure is conducive for a spatial separation of photogenerated charges reducing recombination losses. Band gap energies calculated from absorption spectra indicate potential visible light activity, and this may be due to the orbital mixing of Fe 3d and O 2p as revealed by pre-edge features of X-ray absorption spectra. Band positions are also advantageously placed for a visible light H-2 generation and is indeed found to be the case in methanol-assisted water splitting with standardized hydrogen evolution of similar to 19.5 mmol g(-1) h(-1) for all the catalysts.

}, keywords = {anisotropic structure, H-2 evolution, InFeO3(ZnO)(m), layered oxide, photocatalytic water splitting}, issn = {1944-8244}, doi = {10.1021/am501976z}, author = {Narendranath, Soumya B. and Yadav, Ashok Kumar and Bhattacharyya, Dibyendu and Jha, Shambhu Nath and Devi, R. Nandini} } @article { ISI:000345843700030, title = {Pt States in BaCe0.98Pt0.02O3-delta during start up and shut down operations under different conditions: stability and activity of ionic Pt in water gas shift reaction}, journal = {Catalysis Letters}, volume = {144}, number = {12}, year = {2014}, month = {DEC}, pages = {2227-2232}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Stability of Pt species in doped BaCeO3 perovskites under Water gas shift reaction conditions is studied using X-ray absorption spectroscopy and in situ powder X-ray diffraction. The catalyst BaCe0.98Pt0.02O3-delta has Pt in +2 oxidation state and is found to be stable in the ionic form under reaction conditions as well as under various highly reducing shut down and start up conditions. In-situ XRD under Water Gas shift reaction conditions also reveals the Pt ions to be highly stabilized in lattice and no egress is observed.

}, keywords = {BaCeO3, Deactivation, platinum, WGS reaction, XPS}, issn = {1011-372X}, doi = {10.1007/s10562-014-1378-2}, author = {Rajesh, Thattarathody and Devi, R. Nandini} } @article { ISI:000347498500067, title = {Resistance to ionic pt insertion in oxygen excess LaMnO3 perovskite lattices and its effect in water gas shift reaction}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {395}, year = {2014}, month = {DEC}, pages = {534-542}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Pt doped and impregnated LaMnO3 perovskites are synthesized at different temperatures and Pt and Mn states are compared in an attempt to get insight into extent of lattice incorporation of Pt in perovskite. Various characterization studies indicate that oxygen excess system like LaMnO3 presents substantial resistance to B site doping with Pt. This behavior is different from other oxygen deficient perovskites like LaCoO3 and LaFeO3 in which lattice incorporation stabilizes the active species against sintering. Water gas shift reaction was used as a probe reaction to understand the effect of this difference in the activity. In case of LaMnO3, failure in lattice substitution leads to sintering and deactivation at high synthesis temperatures (\>= 700 degrees C) in both impregnated and doped samples. In doped samples, however, a strong interaction of Pt species with a persistent amorphous phase prevents sintering at lower synthesis temperature thereby enhancing the activity when compared to impregnated sample. The study reveals a possible mechanism in which only Pt(0) species is active with perovskite playing a minimal role in this system due to the resistance to lattice incorporation. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Oxygen excess, Perovskites, Water gas shift reaction, XPS, XRD}, issn = {1381-1169}, doi = {10.1016/j.molcata.2014.08.042}, author = {Rajesh, Thattarathody and Devi, R. Nandini} } @article { ISI:000341619500016, title = {Role of oxygen vacancies in water gas shift reaction: activity study on BaCe0.98-xYxPt0.02O3-delta perovskites}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {36}, year = {2014}, month = {SEP}, pages = {20867-20874}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Oxygen vacancies are suggested to play an important role in reactions like water gas shift where the redox mechanism is crucial. Pt-doped BaCeO3 perovskite, moderately active for water gas shift reaction, is selected for further understanding the role of oxygen vacancies, since perovskite lattice can tolerate and stabilize vacancies facilitating an accurate quantification. Vacancies are created in the system by systematic doping of increasing amounts of Y. Structure and activity studies reveal that the 6\% Y-substituted compound which has the most symmetric B site coordination environment exhibits the highest activity. Hence, it is not the extent of vacancies but their structural characteristics which are found to be decisive. Symmetric coordination around B ions facilitates water adsorption and dissociation by lowering the energy barriers due to the creation of an isotropic environment.

}, issn = {1932-7447}, doi = {10.1021/jp503922x}, author = {Rajesh, Thattarathody and Devi, R. Nandini} } @article { ISI:000349580800008, title = {Effect of b site coordination environment in the ORR activity in disordered brownmillerites Ba2In2-xCexO5+delta}, journal = {ACS Applied Materials \& Interfaces}, volume = {7}, number = {5}, year = {2015}, month = {FEB}, pages = {3041-3049}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Ba2In2O5 brownmillerites in which the In site is progressively doped with Ce exhibit excellent oxygen reduction activity under alkaline conditions. Ce doping leads to structural changes advantageous for the reaction. Twenty-five percent doping retains the ordered structure of brownmillerite with alternate layers of tetrahedra and octahedra, whereas further increase in Ce concentration creates disorder. Structures with disordered oxygen atoms/vacancies are found to be better oxygen reduction reaction catalysts probably aided by isotropic ionic conduction, and Ba2In0.5Ce1.5O5+delta is the most active. This enhanced activity is correlated to the more symmetric Ce site coordination environment in this compound. Stoichiometric perovskite BaCeO3 with the highest concentration of Ce shows very poor activity emphasizing the importance of oxygen vacancies, which facilitate O-2 adsorption, in tandem with catalytic sites in oxygen reduction reactions.

}, keywords = {brownmillerite, fuel cell, oxygen disorder, oxygen reduction reaction, Rietveld refinement}, issn = {1944-8244}, doi = {10.1021/am5087837}, author = {Jijil, Chamundi P. and Bhange, Siddheshwar N. and Kurungot, Sreekumar and Devi, R. Nandini} } @article { ISI:000354137000018, title = {Encapsulation of ultra small metal clusters in silica: evolution of the concept of nanoreactors and the case of Ag-Pd@SiO2 alloy catalyst}, journal = {Catalysis Today}, volume = {251}, year = {2015}, note = {7th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT), Kyoto, JAPAN, JUN 01-06, 2014}, month = {AUG}, pages = {114-120}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The concept of encapsulation of ultra small clusters within silica evolved as a means to address the sintering of active metal nanoparticles and subsequent deactivation observed in supported noble metal catalysts. It is hypothesised that sintering, which mainly occurs due to mobility of metal species on the support surfaces, can be minimised if the growth and movement of metal nanoparticles are constrained. First, nanoparticles are isolated inside 1D channels in 2D mesoporous compounds and the idea develops to complete encapsulation of thiol protected ultra small nanoclusters in silica spheres. Sintering is better controlled in the latter due to the confined space for growth of nanoparticles. Access of reactant molecules to the active metal surfaces also is ensured by porosity created in the silica matrix forming the basis of the concept of nanoreactors. In this paper, we elaborate on the evolution of this concept from our earlier work on highly sinter resistant silica encapsulated Au, Pd and Au-Pd alloys to the present system of Ag-Pd alloy encapsulated in silica. Silver, with the lowest Tammann temperature among noble metals, is highly prone to sintering which is adequately controlled by alloying with Pd as well as encapsulation in silica. Its enhanced activity in paranitrophenol reduction in comparison with pure metals indicates the advantageous effect of alloying. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Ag-Pd alloy, Encapsulation, Sinter resistant, Sintering, Ultra small nanoclusters}, issn = {0920-5861}, doi = {10.1016/j.cattod.2014.11.006}, author = {Mondal, Sourik and Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article { ISI:000349578400018, title = {Surface site modulations by conjugated organic molecules to enhance visible light activity of ZnO nanostructures in photocatalytic water splitting}, journal = {Journal of Physical Chemistry C}, volume = {119}, number = {6}, year = {2015}, month = {FEB}, pages = {3060-3067}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Surface modification of ZnO nanoparticles is identified as a method of modulating surface sites advantageously. ZnO nanoparticles of two different sizes are surface modified with a conjugated organic moiety to enable electron conduction and transfer. Enhanced H-2 evolution from water-methanol mixtures was observed in the composite systems compared to pristine ZnO under visible light irradiation without any cocatalyst. The system is also marginally active in water splitting in pure water without any sacrificial agents. Photophysical characterization indicates that even though reducing size into the nanoregime affects the band gap detrimentally, modifications by simple conjugated organic molecules assist in enhanced visible light activity. The experimental observations are corroborated with computational studies, which also point to a localization of valence band maximum of the interface on the organic moiety and conduction band minimum on ZnO.

}, issn = {1932-7447}, doi = {10.1021/jp511996z}, author = {George, Leena and Sappati, Subrahmanyam and Ghosh, Prasenjit and Devi, R. Nandini} } @article {43020, title = {Nitrogen doping in oxygen-deficient Ca2Fe2O5: a strategy for efficient oxygen reduction oxide catalysts}, journal = {ACS Applied Materials and Interfaces}, volume = {8}, year = {2016}, month = {NOV}, pages = {34387{\textendash}34395}, doi = {10.1021/acsami.6b11718}, author = {Jijil, Chamundi P. and Lokanathan, Moorthi and Chithiravel, Sundaresan and Nayak, Chandrani and Bhattacharyya, Dibyendu and Jha, Shambhu Nath and Babu, P. D. and Kakade, Bhalchandra A. and Devi, R. Nandini} } @article { ISI:000372684900009, title = {Photocatalytic H-2 evolution from water-methanol mixtures on InGaO3(ZnO)(m) with an anisotropic layered structure modified with CuO and NiO cocatalysts}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {415}, year = {2016}, month = {MAY}, pages = {82-88}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

InGaO3(ZnO)(m) series of oxides is found to be active for photocatalytic H-2 evolution from water-methanol mixtures. The structure of this series is highly anisotropic with InO6 octahedral layers sandwiching Ga/ZnOn polyhedra. The structural anisotropy in which the conducting layer is spatially separated from the charge generation sites may help in suppressing charge recombination and consequently enhance catalytic activity. The band gaps of the series obtained from absorption spectra are above 3.6 eV and hence they are not active under visible light irradiation. H-2 evolution is considerably enhanced under UV light on employing NiO as cocatalyst due to facile electron transfer from InGaO3(ZnO)(m). to NiO. However, when CuO is used as cocatalyst, visible light activity could be brought out. Due to the very low band gap of CuO, it can act as a sensitizer absorbing in visible light. The band positions become conducive for H-2 evolution due to band alignments consequent to electron accumulation in CuO conduction band. (C) 2016 Elsevier B.V. All rights reserved.

}, keywords = {InGaO3(ZnO)(m), photocatalytic water splitting, visible light, XPS, XRD}, issn = {1381-1169}, doi = {10.1016/j.molcata.2016.01.018}, author = {Narendranath, Soumya B. and Thekkeparambil, Saranya V. and George, Leena and Thundiyil, Shibin and Devi, R. Nandini} } @article { ISI:000381436500019, title = {Understanding the electron transfer process in ZnO-naphthol azobenzoic acid composites from photophysical characterisation}, journal = {Physical Chemistry Chemical Physics}, volume = {18}, number = {32}, year = {2016}, month = {AUG}, pages = {22179-22187}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Semiconductor nanoparticles surface modified with organic molecules capable of visible light absorption and effectively transferring the electrons to the catalytic sites have the potential to be good photocatalysts. ZnO nanoparticles of size similar to 3 nm are grafted with two azonaphthols, one conjugated and the other non-conjugated. The photophysical properties of modified ZnO indicate an effective electron transfer from the conjugated azonaphthol to ZnO but not in the case of the non-conjugated molecule. It is also observed from lifetime studies that the conjugated molecule stabilises the defect sites on ZnO nanoparticles. It is possible that excited electrons from the conjugated molecule are transferred to specific defect sites in ZnO. This apparently does not occur in the non-conjugated molecule, bringing to focus the importance of the photophysical characteristics of organic modifiers in designing visible light active photocatalysts.

}, issn = {1463-9076}, doi = {10.1039/c6cp02908f}, author = {George, Leena and Kunhikannan, Athira K. and Illathvalappil, Rajith and Ottoor, Divya and Kurungot, Sreekumar and Devi, R. Nandini} } @article {45831, title = {Valorization of coffee bean waste: a coffee bean waste derived multifunctional catalyst for photocatalytic hydrogen production and electrocatalytic oxygen reduction reactions}, journal = {RSC Advances}, volume = {6}, year = {2016}, month = {AUG}, pages = {82103-82111}, type = {Article}, abstract = {

Here, we report the valorization of coffee bean waste (CBW) by producing nitrogen doped porous carbon (p-Cof) having both photocatalytic and electrocatalytic properties using a silica templating method. Morphological investigation of p-Cof reveals the presence of assemblies of highly porous flat carbon blocks. p-Cof exhibits a high surface area (1213 m(2) g(-1)) and a wide range of micro-and mesopores with good electrical conductivity. Along with this, the surface of p-Cof displays the presence of graphitic and pyridone-type nitrogen coordinations, which help p-Cof to perform as a multifunctional catalyst as revealed from its catalytic activities towards photocatalytic hydrogen production (PHP) and electrocatalytic oxygen reduction reactions. p-Cof produces 334 mu mol h(-1) g(-1) of hydrogen from water under visible light and 575 mmol h(-1) g(-1) of hydrogen under solar light irradiation with excellent stability. Along with this, p-Cof also displays improved oxygen reduction reaction (ORR) activity in alkaline medium. A better onset potential (0.91 V vs. RHE) and half-wave potential (0.75 V vs. RHE) are displayed by p-Cof compared to the catalyst derived from the simple annealing of CBW without employing the silica template. Along with the better electrochemical activity, p-Cof shows excellent ORR kinetics and electrochemical stability compared to the current state-of-the-art Pt/C.

}, issn = {2046-2069}, doi = {10.1039/c6ra14907c}, author = {Unni, SreeKuttan M. and George, Leena and Bhange, Siddheshwar N. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {44411, title = {Ultra small nanoclusters to nanoparticles: fine tuning of particle size in water dispersible cation functionalized thiolate protected Pd system}, journal = {Materials Today-Proceedings}, volume = {4}, year = {2017}, month = {MAR}, pages = {9440-9444}, abstract = {Monolayer protected noble metal nanoparticles have attracted considerable attention in the past decade with potential applications in fields ranging from catalysis to biosensors [1, 2,]. We have developed a novel procedure for the synthesis of water dispersible Pd nanoparticles based on a bifunctional ligand, N,N,N-tripropyl(11-mercaptoundecyl) ammonium chloride in which thiol group binds to the metal, hydrophobic middle alkyl chain acts as capping agent and provides steric stability and on the other end the ammonia group helps in making nanoparticles hydrophilic. In this paper, we report the fine-tuning of size of water dispersible Pd nanosystems ranging from clusters to nanoparticles by adjusting the synthetic parameters and their characterization. (C) 2017 Elsevier Ltd. All rights reserved.}, author = {Dhanraj, Prakriti and Samanta, Anupam and Devi, R. Nandini} } @article {44087, title = {Understanding alloy structure and composition in sinter-resistant AgPd@SiO2 encapsulated catalysts and their effect on catalytic properties}, journal = {New Journal of Chemistry}, volume = {41}, year = {2017}, month = {DEC}, pages = {14652-14658}, type = {Article}, abstract = {The extent of alloying and the alloy composition, which are crucial in determining the activity and selectivity of bimetallic catalysts, were studied in porous silica encapsulated AgPd catalysts using XRD, HRTEM and HAADF-STEM. Water-dispersible ligand protected Pd ultra-small clusters and Ag nanoparticles of three different sizes were used as the precursors. The high reactivity of Pd ultra-small clusters enhanced the alloying of larger Ag nanoparticles to some extent. Encapsulation appeared to have minimised the sintering of the resultant nanoparticles. The earlier suggestions of the role of d-band positions with respect to adsorption energies holds good for the AgPd system and alloying enhances the activity. Alloy with the composition of Ag50Pd50 was found to be the most active with the reaction rate enhanced two fold compared to that in other compositions. Other factors like particle size and sinter-resistance also played important roles in enhancing the activity of these catalysts.}, doi = {10.1039/c7nj03652c}, author = {Mondal, Sourik and Rajesh, Thattarathody and Dhar, Basab B. and Snellman, Markus and Li, Junjie and Deepak, Francis Leonard and Devi, R. Nandini} } @article {44336, title = {Sensitizing with short conjugated molecules: multimodal anchoring on ZnO nanoparticles for enhanced electron transfer characteristics, stability and H-2 evolution}, journal = {Catalysis Today}, volume = {309}, year = {2018}, month = {JUL}, pages = {89-97}, type = {Article}, abstract = {Sensitizing semiconductors with organic dyes is usually employed to improve efficiency of semiconductors towards visible light absorption and charge transport. However, till date most of the dyes are either noble metal based with complex and expensive synthesis procedure or have a very narrow absorption band. Further the photostability of the dyes is another important issue. In this work we have studied, using a combination of photophysical and computational methods, ZnO nanoparticles sensitized with transition metal free, cheap and easy to synthesize azoquinoline dye that has been designed to have multiple chelating sites, viz., carboxylic group and hydroxyl imine group as a photocatalyst for water splitting activity. We find that the presence of multiple chelating sites facilitates dual mode of anchoring on ZnO nanoparticles, which leads to enhanced photostability and H-2 generation of the composite. This is attributed to the incorporation of resonance features in the dye that increases electron transfer between ZnO and dye in contrast to the charge accumulation and photo degradation observed in non-conjugated and single site anchoring counterparts. Electron transfer from ZnO to dye under UV light and reverse in visible light could be identified experimentally. Such simple designing aspects can aid in identifying better catalysts for photocatalytic water splitting.}, doi = {10.1016/j.cattod.2017.09.052}, author = {George, Leena and Sappati, Subrahmanyam and Ghosh, Prasenjit and Devi, R. Nandini} } @article {46420, title = {Descriptors to predict dye-sensitized semiconductor based photocatalyst for hydrogen evolution reaction}, journal = {ChemCatChem}, year = {2019}, type = {Article; Early Access}, abstract = {

Discovering efficient photocatalysts for hydrogen production from water splitting is highly desirable. Computational studies can help in rational designing of such catalysts through high throughput screening of materials. However, for that purpose one needs to identify descriptors that not only connects material properties with their functionality but are easy and inexpensive to compute. Using a combination of density functional theory based calculations and experiments we show two descriptors, namely, charge injection efficiency and electron hole separation, that can be used for in silico design of new and efficient dye-sensitized-semiconductor composites as catalysts for hydrogen evolution reaction.

}, keywords = {charge injection, descriptor, dye-sensitized semiconductors, electron-hole separation, H-2 evolution}, issn = {1867-3880}, doi = {10.1002/cctc.201901924}, author = {Sappati, Subrahmanyam and George, Leena and Swamy, Vincent Paul and Devi, R. Nandini and Ghosh, Prasenjit} } @article {46845, title = {Hierarchical nanoflower arrays of Co9S8-Ni3S2 on nickel foam: a highly efficient binder-free electrocatalyst for overall water splitting}, journal = {Chemistry-A European Journal}, volume = {26}, year = {2020}, month = {JUN }, pages = {7900-7911}, type = {Article}, abstract = {

Hydrogen production is vital for meeting future energy demands and managing environmental sustainability. Electrolysis of water is considered as the suitable method for H-2 generation in a carbon-free pathway. Herein, the synthesis of highly efficient Co9S8-Ni3S2 based hierarchical nanoflower arrays on nickel foam (NF) is explored through the one-pot hydrothermal method (Co9S8-Ni3S2/NF) for overall water splitting applications. The nanoflower arrays are self-supported on the NF without any binder, possessing the required porosity and structural characteristics. The obtained Co9S8-Ni3S2/NF displays high hydrogen evolution reaction (HER), as well as oxygen evolution reaction (OER), activities in 1 m KOH solution. The overpotentials exhibited by this system at 25 mA cm(-2) are nearly 277 and 102 mV for HER and OER, respectively, in 1 m KOH solution. Subsequently, the overall water splitting was performed in 1 m KOH solution by employing Co9S8-Ni3S2/NF as both the anode and cathode, where the system required only 1.49, 1.60, and 1.69 V to deliver the current densities of 10, 25, and 50 mA cm(-2), respectively. Comparison of the activity of Co9S8-Ni3S2/NF with the state-of-the-art Pt/C and RuO2 coated on NF displays an enhanced performance for Co9S8-Ni3S2/NF both in the half-cell as well as in the full cell, emphasizing the significance of the present work. The post analysis of the material after water electrolysis confirms that the surface Co(OH)(2) formed during the course of the reaction serves as the favorable active sites. Overall, the activity modulation achieved in the present case is attributed to the presence of the open-pore morphology of the as formed nanoflowers of Co9S8-Ni3S2 on NF and the simultaneous presence of the surface Co(OH)(2) along with the highly conducting Co9S8-Ni3S2 core, which facilitates the adsorption of the reactants and subsequently its conversion into the gaseous products during water electrolysis.

}, keywords = {cobalt sulfide, electrocatalysts, Hydrogen evolution, overall water splitting, oxygen evolution}, issn = {0947-6539}, doi = {10.1002/chem.202000839, Early Access Date = MAY 2020}, author = {Illathvalappil, Rajith and Walko, Priyanka S. and Kanheerampockil, Fayis and Bhat, Suresh K. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {46777, title = {Role of B site ions in bifunctional oxygen electrocatalysis: a structure-property correlation study on doped Ca(2)Fe(2)O(5)brownmillerites}, journal = {Physical Chemistry Chemical Physics}, volume = {22}, year = {2020}, month = {JUL }, pages = {15520-15527}, type = {Article}, abstract = {

The role of B site doping with transition metals in brownmillerites, a perovskite related family of compounds, in bifunctional oxygen electrocatalysis,viz., simultaneous reduction and evolution reactions, is analysed. Ca2Fe1.9M0.1O5(M = Mn, Co, Ni, and Cu) is synthesised and structurally characterised by powder XRD and Rietveld refinement. Valence states of the surface B site ions are identified by X-ray photoelectron spectroscopy. Bifunctional oxygen electrochemistry is studied with the RDE and RRDE techniques and correlated with the structural and electronic parameters like oxygen non-stoichiometry and B site catalytic activity. Since the widely accepted electronic descriptors like e(g)filling may not be sufficient for explaining the bifunctional activity, B site electron donating capability as well as the extent of oxygen vacancies enhancing O(2)adsorption is also considered. Such structural parameters are also found to influence both the ORR and OER and based on this, Ni doping is proposed as advantageous for the bifunctional activity.

}, issn = {1463-9076}, doi = {10.1039/d0cp02391d}, author = {Thundiyil, Shibin and Vinod, C. P. and Kurungot, Sreekumar and Devi, R. Nandini} } @article {46920, title = {Understanding alloy structure and composition in sinter-resistant AgPd@SiO2 encapsulated catalysts and their effect on catalytic properties (vol 41, pg 14652, 2017)}, journal = {New Journal of Chemistry}, volume = {44}, year = {2020}, month = {MAR }, pages = {4664}, type = {Correction}, issn = {1144-0546}, doi = {10.1039/d0nj90031a}, author = {Mondal, Sourik and Rajesh, Thattarathody and Dhar, Basab B. and Snellman, Markus and Li, Junjie and Deepak, Francis Leonard and Devi, R. Nandini} } @article {46978, title = {Variations in activity of Ru/TiO(2 )and Ru/Al2O3 catalysts for CO2 hydrogenation: an investigation by in-situ infrared spectroscopy studies}, journal = {Molecular Catalysis}, volume = {482}, year = {2020}, month = {FEB}, pages = {110700}, type = {Article}, abstract = {

CO2 hydrogenation to methane, an important reaction strategically and also for value adding to CO2, is investigated on two different catalysts, Ru supported on alumina as well as titania to understand better low temperature activity of Ru/TiO2 catalyst. In-situ infrared studies are carried out in three different steps, viz., (i) CO2 adsorption on fully reduced catalyst (ii) reaction of these adsorbed species with gaseous H-2 and (iii) under co-feed of CO2 and H-2, at different temperatures. On Ru/Al2O3 catalyst, CO2 reacts with hydroxyls on the support surface to form carbonate and adsorbs reductively on metal as CO. Further reduction to formate and methyl species occurs on reaction with H. Small concentration of the reactive intermediate formyl forms only at high temperatures. Whereas, bare TiO2 itself seems capable of reductive adsorption of CO2 as formate indicating enhanced reducibility of titania based catalyst. Formyl groups are observed at low temperatures in Ru/TiO2 in step (ii), which further forms methyl and gaseous methane at much lower temperatures when compared to alumina catalyst. Highly reactive CO species loosely bound to metal-support interface observed at high temperatures, which is not present on Ru/Al2O3 catalyst also makes this catalyst superior. In comparison, linearly bound CO seen in alumina catalyst is not as reactive.

}, keywords = {CO2 hydrogenation, In-situ infra red spectroscopy, Ru/Al2O3, Ru/TiO2}, issn = {2468-8231}, doi = {10.1016/j.mcat.2019.110700}, author = {Dongapure, Pavan and Bagchi, Sayan and Mayadevi, S. and Devi, R. Nandini} } @article {47110, title = {Efficient electrochemical oxygen reduction to hydrogen peroxide by transition metal-doped silicate Sr0.7Na0.3SiO3-delta}, journal = {ACS Applied Materials \& Interfaces}, volume = {13}, year = {2021}, month = {JAN}, pages = {382-390}, type = {Article}, abstract = {

Electrochemical oxygen reduction in a selective two-electron pathway is an efficient method for onsite production of H2O2. State of the art noble metal-based catalysts will be prohibitive for widespread applications, and hence earth-abundant oxide-based systems are most desired. Here we report transition metal (Mn, Fe, Ni, Cu)-doped silicates, Sr0.7Na0.3SiO3-delta, as potential electrocatalysts for oxygen reduction to H2O2 in alkaline conditions. These novel compounds are isostructural with the parent Sr0.7Na0.3SiO3-delta and crystallize in monoclinic structure with corner-shared SiO4 groups forming cyclic trimers. The presence of Na stabilizes O vacancies created on doping, and the transition metal ions provide catalytically active sites. Electrochemical parameters estimated from Tafel and Koutechy-Levich plots suggest a two-electron transfer mechanism, indicating peroxide formation. This is confirmed by the rotating ring disc electrode method, and peroxide selectivity and Faradaic efficiency are calculated to be in the range of 65-82\% and 50-68\%, respectively, in a potential window 0.3 to 0.6 V (vs RHE). Of all the dopants, Ni imparts the maximum selectivity and efficiency as well as highest rate of formation of H2O2 at 1.65 mu mol s(-1).

}, keywords = {H2O2, mixed metal oxide, ORR, silicate}, issn = {1944-8244}, doi = {10.1021/acsami.0c16311}, author = {Thundiyil, Shibin and Kurungot, Sreekumar and Devi, R. Nandini} } @article {47498, title = {Red fluorescent ultra-small gold nanoclusters functionalized with signal molecules to probe specificity in quorum sensing receptors in gram-negative bacteria}, journal = {Archives of Microbiology}, year = {2021}, month = {JUN}, type = {Article; Early Access}, abstract = {Ultra-small (size < 2 nm) gold nanoclusters (AuNCs) are used as fluorescent probes which have excellent applications in bioimaging and sensing due to their emission in visible and NIR spectral region. Here, this property is exploited for understanding the quorum sensing phenomenon in bacteria which is regulated by signal molecules which are specific to various species. AuNCs are then functionalized with the signal molecules, Acyl Homoserine Lactones (AHL) of varying carbon chain length, C-6, C-8, and C-12 without 3rd C modification, to sense different strains of gram-negative bacteria i.e., Escherichia coli, Cronobacter sakazakii and Pseudomonas aeruginosa. In the concentration employed, selectivity to a limited extent is observed between the three Gram-negative bacteria tested. E. coli showed emission with all the AHL conjugates and P. aeruginosa did not interact with any of the three conjugates, whereas C. sakazakii showed specificity to C-8AHL. This is probably due to selectivity for cognate AHL molecules of appropriate concentrations.}, keywords = {acyl homoserine lactone, fluorescence imaging, Gold nanoclusters, quorum sensing, Receptors, selectivity}, issn = {0302-8933}, doi = {10.1007/s00203-021-02338-y, Early Access Date = JUN 2021}, author = {Chahande, Anurag M. and Lathigara, Disha and Prabhune, Asmita A. and Devi, R. Nandini} } @article {47311, title = {Synergistic effect of B site co-doping with Co and Ce in bifunctional oxygen electrocatalysis by oxygen deficient brownmillerite Ba2In2O5}, journal = {Catalysis Today}, volume = {375}, year = {2021}, month = {SEP}, pages = {494-500}, type = {Article}, abstract = {

Specificity in oxygen reduction and evolution reactions is pivotal in bifunctional catalysts in advanced energy devices which are expected to be active in a wide potential window and stable in both electrochemically reducing and oxidising atmospheres. State of the art noble metal catalysts for these reactions are fraught with issues whereas, metal oxides are expected to be stable in large potential window and can be tuned to have better bifunctional activity. Catalytically active metals, redox centres, oxygen vacancies etc. are some of the features of structured oxides which can be exploited in oxygen electrocatalysis. Brownmillerite family of compounds with general formula, A2B2O5\ has high concentrations of ordered oxygen vacancy in a layer and can be promising bifunctional oxygen electrocatalysts, by appropriate B site doping. Ba2In2O5\ is a well-studied system for its oxide ion conductivity and proximity of active B sites to O vacancies provide good O adsorption sites which are catalytically active. Here, cobalt and cerium are co-doped in Ba2In2O5, anticipating a synergistic effect of Ce(III)/Ce(IV) redox centre in ORR and Co activity in OER along with O vacancies providing adsorption sites. We have studied the structural changes associated with the doping by Rietveld refinement of the XRD patterns and correlated the structure to bifunctional oxygen electrocatalytic activity which is found to enhance on increasing the Co and Ce content.

}, doi = {10.1016/j.cattod.2020.05.046}, author = {Thundiyil, Shibin and Kurungot, Sreekumar and Devi, R. Nandini} } @article {47592, title = {Tuning the selectivity of CO2 hydrogenation using ceramic hollow fiber catalytic modules}, journal = {Reaction Chemistry \& Engineering}, volume = {6}, year = {2021}, month = {SEP }, pages = {1655-1665}, type = {Article}, abstract = {The unique structural features and advantageous pore distributions of alumina hollow fibers can be exploited to tune the selectivity in heterogeneous catalysis. Formation of a finger-like cavity structure is the unique characteristic of the phase inversion method, which provides a larger surface area to volume ratio desirable for catalytic reactions. This feature, along with a highly porous sandwiched skin layer, makes this architecture superior to conventional powder catalysts or other structured catalyst forms like monoliths. Alumina hollow fibers are prepared by the modified phase inversion method and characterized for their pore size and distribution. Ni metal nanoparticles are uniformly deposited in the Al2O3 hollow fibers to prepare a Ni/Al2O3 catalyst and tested for the CO2 methanation reaction. Suitable reactor and catalyst loading methods are designed and optimized to achieve higher CO2 to methane conversion in a temperature range of 225 to 400 degrees C. The alpha-alumina phase, which is usually reported to be a poor support for Ni in CO2 methanation in the conventional fixed bed configuration, showed high activity when modulated as hollow fibers. Also, the selectivity to CH4 is enhanced and minimal CO formation is observed. The kinetic rate expressions are simulated for the prediction of methane and CO gas evolution at the outlet with temperature. The experimental results for the gas composition are in good agreement with the model predictions. The advantage of such a module reactor is explained based on the mass transfer limitations and consequently the reaction time constants arrived at from the predicted gas compositions.}, issn = {2058-9883}, doi = {10.1039/d1re00076d}, author = {Jogdand, Shunottara M. and Bedadur, Prachiti R. and Torris, Arun and Kharul, Ulhas K. and Naidu, V. Satyam and Devi, R. Nandini} } @article {48353, title = {Addressing challenges in sealing of scalable multifiber module for O-2 enrichment using LSCF membranes}, journal = {International Journal of Applied Ceramic Technology}, volume = {19}, year = {2022}, month = {MAY}, pages = {1561-1571}, type = {Article}, abstract = {

Scalable and multifiber modules in oxygen separation face huge challenges due to difficulty in integrating all the necessary components, especially in sealing the fibers in a gas tight module. Here, we report our findings on design and fabrication of a multifiber La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF)-based module, which can be scaled up. The focus is on sealing ceramic-metal interfaces by layering of sealants of varying thermal properties. We have also incorporated the use of dead ended fibers to minimize ceramic-metal interfaces in the hot zones and present a new method for dead ending by flame melting. Pressurizing the air inlet feed from either bore side or shell side is detrimental to the structural integrity of the fibers. A thorough characterization of the fresh and spent fibers is also carried out using X-ray tomography and electron microscopy, which indicates effect of temperature and pressure on the fibers.

}, keywords = {Characterization, permeability, Perovskites}, issn = {1546-542X}, doi = {10.1111/ijac.13967}, author = {Jogdand, Shunottara M. and Bedadur, Prachiti R. and Torris, Arun and Agrawal, Ravi and Kharul, Ulhas K. and Devi, R. Nandini} } @article {48122, title = {Co-Ni layered double hydroxide for the electrocatalytic oxidation of organic molecules: an approach to lowering the overall cell voltage for the water splitting process}, journal = {ACS Applied Materials \& Interfaces}, volume = {14}, year = {2022}, month = {APR}, pages = {16222-16232}, type = {Article}, abstract = {

Electrocatalytic oxidation of simple organic molecules oilers a promising strategy to combat the sluggish kinetics of the water oxidation reaction (WOR). The low potential requirement, inhibition of the crossover of gases, and formation of value-added products at the anode are benefits of the electrocatalytic oxidation of organic molecules. Herein, we developed cobalt-nickel-based layered double hydroxide (LDH) as a robust material for the electrocatalytic oxidation of alcohols and urea at the anode, replacing the WOR. A facile synthesis protocol to form LDHs with different ratios of Co and Ni is adapted. It demonstrates that the reactants could be efficiently oxidized to concomitant chemical products at the anode. The half-cell study shows an onset potential of 1.30 V for benzyl alcohol oxidation reaction (BAOR), 1.36 V for glycerol oxidation reaction (GOR), 1.33 V for ethanol oxidation reaction (EOR), and 1.32 V for urea oxidation reaction (UOR) compared with 1.53 V for WOR. Notably, the hybrid electrolyzer in a full-cell configuration significantly reduces the overall cell voltage at a 20 mA cm(-2) current density by similar to 15\% while coupling with the BAOR, EOR, and GOR and similar to 12\% with the UOR as the anodic half-cell reaction. Furthermore, the efficiency of hydrogen generation remains unhampered with the types of oxidation reactions (alcohols and urea) occurring at the anode. This work demonstrates the prospects of lowering the overall cell voltage in the case of a water electrolyzer by integrating the hydrogen evolution reaction with suitable organic molecule oxidation.

}, keywords = {electrocatalytic oxidation, energy conversion, imidazole mediated, Layered compounds, water splitting}, issn = {1944-8244}, doi = {10.1021/acsami.2c00982}, author = {Shilpa, Nagaraju and Pandikassala, Ajmal and Krishnaraj, Perayil and Walko, Priyanka S. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {48012, title = {Effect of B site substitution in Gd2B2-xNiyO7-delta (B= Ti, Zr) ternary metal oxide catalysts in dry reforming of methane}, journal = {Molecular Catalysis}, volume = {522}, year = {2022}, month = {APR}, pages = {112242}, type = {Article}, abstract = {

Structured catalysts are emerging as active and durable catalysts in dry reforming of methane due to their inherent characteristics like lattice insertion of active metals and consequent stability imparted. Here we report Ti and Zr substituted Gd2B2-xNiyO7-delta (B = Ti, Zr) catalysts synthesized by citrate gel method, which are characterized and tested for dry reforming of methane. Structure and Ni substitution has been confirmed by Rietveld refinement of powder XRD patterns and Raman analysis. TPR and CO2-TPD were performed to analyze the reducibility and effect of basic sites of catalysts in DRM activity. Ni doped Ti analogue shows stable and superior activity towards dry reforming of methane for 100 h. The in situ IR studies and XPS analysis confirmed the presence of surface hydroxyl species in this catalyst, which triggers the activation of CO2 and provides higher and durable activity in dry reforming reaction. Absence of any C formation in this catalyst after durability test indicates the mechanism of C gasification by the surface hydroxyl species enhancing stable activity for long durations.

}, keywords = {A(2)B(2)O(7), Citrate gel method, Dry reforming of methane, Ternary metal oxide}, issn = {2468-8231}, doi = {10.1016/j.mcat.2022.112242}, author = {Ghodke, Seema R. and Thundiyil, Shibin and Dongapure, Pavan and Devi, R. Nandini} } @article {47826, title = {Tuning of oxygen reduction pathways through structural variation in transition metal-doped Ba2In2O5}, journal = {ChemElectroChem}, volume = {9}, year = {2022}, month = {JAN}, pages = {e202101163}, type = {Article}, abstract = {Abstract Oxygen reduction reaction (ORR) can take place either through a two-electron pathway to form H2O2 or through a four-electron pathway to form H2O. Both the reactions are important in the respective fields, viz., H2O2 production as well as fuel cell technology, and rational design of catalysts is mandatory to acquire high energy efficiency in both cases. Here, we report the structure-electrochemical property correlation of a series of perovskite related brownmillerite compounds, Ba2In0.75M0.25O5 (M=Mn/Fe/Co/Ni/Cu), synthesized by solid-state method. On transition metal doping, octahedral distortions were observed, and the highly disordered material tends to follow the 4e transfer mechanism. More symmetrical structures followed the 2e pathway to form H2O2 as the product with high peroxide selectivity. The distortion in the octahedral arrangement can be a descriptor to finetune the selectivity of the catalysts towards the 2e and 4e pathways of ORR.}, keywords = {brownmillerite, Descriptors, Electrochemical H2O2 synthesis, Octahedral distortion, oxygen reduction reaction}, doi = {10.1002/celc.202101163}, author = {Thundiyil, Shibin and Pandikassala, Ajmal and Kurungot, Sreekumar and Devi, R. Nandini} } @article {48935, title = {Active site engineering and theoretical aspects of {\textquoteleft}{\textquoteleft}Superhydrophilic{\textquoteright}{\textquoteright} nanostructure array enabling efficient overall water electrolysis}, journal = {Small}, volume = {19}, year = {2023}, month = {DEC}, type = {Article}, abstract = {

The rational design of noble metal-free electrocatalysts holds great promise for cost-effective green hydrogen generation through water electrolysis. In this context, here, the development of a superhydrophilic bifunctional electrocatalyst that facilitates both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline conditions is demonstrated. This is achieved through the in situ growth of hierarchical NiMoO4@CoMoO4 center dot xH(2)O nanostructure on nickel foam (NF) via a two-step hydrothermal synthesis method. NiMoO4@CoMoO4 center dot xH(2)O/NF facilitates OER and HER at the overpotentials of 180 and 220 mV, respectively, at the current density of 10 mA cm(-2). The NiMoO4@CoMoO4 center dot xH(2)O/NF parallel to NiMoO4@CoMoO4 center dot xH(2)O/NF cell can be operated at a potential of 1.60 V compared to 1.63 V displayed by the system based on the Pt/C@NF parallel to RuO2@NF standard electrode pair configuration at 10 mA cm(-2) for overall water splitting. The density functional theory calculations for the OER process elucidate that the lowest Delta G of NiMoO4@CoMoO4 compared to both Ni and NiMoO4 is due to the presence of Co in the OER catalytic site and its synergistic interaction with NiMoO4. The preparative strategy and mechanistic understanding make the windows open for the large-scale production of the robust and less expensive electrode material for the overall water electrolysis.

}, keywords = {density functional theory (DFT) study, hydrogen evolution reaction (HER), Hydrothermal synthesis, oxygen evolution reaction (OER), superhydrophilic nanostructures, synergistic interaction, water electrolysis}, issn = {1613-6810}, doi = {10.1002/smll.202304143}, author = {Barik, Sidharth and Kharabe, Geeta Pandurang and Illathvalappil, Rajith and Singh, Chandrodai Pratap and Kanheerampockil, Fayis and Walko, Priyanka S. and Bhat, Suresh K. and Devi, R. Nandini and Vinod, C. P. and Krishnamurty, Sailaja and Kurungot, Sreekumar} } @article {48309, title = {Cobalt-manganese modified theophrastite phase of nickel hydroxide nanoflower arrays on nickel foam as a self-standing bifunctional electrode for overall water electrolysis}, journal = {Sustainable Energy \& Fuels}, volume = {7}, year = {2023}, month = {MAY}, pages = {2428-2440}, type = {Article}, abstract = {

Designing and developing self-supported electrodes for water electrolysis is attractive as compared to conventional catalyst-coated electrodes. Herein, a (Co0.3Mn0.1Ni0.6)(OH)(2)/NF nanocomposite is prepared by anchoring (Co0.3Mn0.1Ni0.6)(OH)(2)via simple one-pot hydrothermal synthesis on nickel foam. The presence of Mn induces the external electronic structure of Co(OH)(2), and this also improves the electrochemically active surface area (ECSA). These favor better accessibility of active sites and increased intrinsic activity for the OER and HER. (Co0.3Mn0.1Ni0.6)(OH)(2)/NF has shown promising electrochemical activity toward the OER and HER in a 1 M KOH electrolyte, with an overpotential of 270 mV for the OER and 163 mV for the HER to deliver 10 mA cm(-2) current density. The overall water splitting was performed by employing (Co0.3Mn0.1Ni0.6)(OH)(2)/NF as both the cathode and anode by displaying a voltage of 1.62 V at 10 mA cm(-2), which is comparable to that extracted from a similar system based on the state-of-the-art Pt/C@NF cathode and RuO2@NF anode (1.60 V at 10 mA cm(-2)) standard electrode pair. Interestingly, at high current densities, the (Co0.3Mn0.1Ni0.6)(OH)(2)/NF//(Co0.3Mn0.1Ni0.6)(OH)(2)/NF system displayed better overall water splitting performance (1.78 V at 100 mA cm(-2)) compared to its Pt/C@NF//RuO2@NF (1.89 V at 100 mA cm(-2)) counterpart while displaying a stable output during the evolution period that lasted for 24 h. The amounts of H-2 and O-2 produced are estimated to be 701.2 and 358.6 mmol, respectively, at a time interval of 1 h; these amounts correspond to an similar to 1 : 2 ratio of O-2 and H-2, respectively. This study confirms the capability for employing (Co0.3Mn0.1Ni0.6)(OH)(2)/NF as a bi-functional and self-standing electrode for the realistic demonstrations of overall water splitting applications.

}, issn = {2398-4902}, doi = {10.1039/d3se00233k}, author = {Kharabe, Geeta Pandurang and Illathvalappil, Rajith and Barik, Sidharth and Kanheerampockil, Fayis and Walko, Priyanka S. and Bhat, Suresh K. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {48756, title = {Mechanistic insights into near ambient pressure activity of intermetallic NiZn/TiO2 catalyst for CO2 conversion to methanol}, journal = {ChemCatChem}, volume = {15}, year = {2023}, month = {JAN }, type = {Article}, abstract = {

Ni-Zn pair is predicted through descriptor-based studies to be conducive for CO2 hydrogenation. In this study, NiZn (1 : 1) intermetallics supported on TiO2 is identified as a potential candidate for near ambient pressure activity. The effect of reduction temperature on the catalyst textural properties as well as on CO2 to methanol reduction are explored. Structural and microscopic studies provide clear evidence of phase evolution of NiZn alloy with increasing reduction temperatures, along with phase variations of Zn based oxides. Interface between NiZn intermetallics and ZnO nanoparticles observed at reduction temperature of 550 degrees C, seems to play a crucial role in making this system most active and selective to methanol. In addition, in-situ IR studies provide mechanistic insights and indicates the formation of methanolic species even at ambient pressure.

}, keywords = {CCUS, CO2, In-situ IR, Methanol, near ambient pressure}, issn = {1867-3880}, doi = {10.1002/cctc.202201150}, author = {Dongapure, Pavan and Tekawadia, Jyoti and Thundiyil, Shibin and Caha, Ihsan and Deepak, Francis Leonard and Devi, R. Nandini} } @article {48462, title = {Scalable optical fiber reactor for photocatalytic H2 production: addressing scattering issues}, journal = {International Journal of Hydrogen Energy}, volume = {48}, year = {2023}, month = {MAY}, pages = {17086-17096}, type = {Article}, abstract = {

Scattering is one of the main challenges in scaling up photocatalytic water splitting using the most prevalent powder catalysts. This can be overcome by decoupling the reaction medium from light transmission, as in the case of optical fibers. Here we explore utilizing optical fibers coated with 5 wt\% CuO supported on TiO2 for photocatlytic H2 production from water-methanol mixtures. CuO/TiO2 is a well studied photo catalyst in which photoreduced Cu species are known to act as sensitizers for inducing visible light activity. Lower activity of sequentially coated systems indicates that appropriate interfaces of active Cu and TiO2 with water are desirable. The scalability of such optical fiber-based systems along with potential in non-potable turbid water media are demonstrated. Maximum activity of 22 mmoles of H2 in 8 h was obtained with 50 mg of catalyst coated on optical fibers, which increases linearly with increase in fiber numbers, whereas, drastic reduction in activity is observed in powder catalyst upon increasing the catalyst quantity. A one-to-one comparison of 700 mg of catalyst in powder form and coated on optical fibers indicates more than one order enhancement in activity in the optical fiber based system. In addition, -70\% retention in activity in highly turbid non-potable water was observed as compared to powdered system which shows complete reduction in the activity by 99.99\%. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

}, keywords = {CuO, Optical fibers, photocatalytic water splitting, TiO2, Total internal reflection, Visible light utilisation}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2023.01.148}, author = {Walko, Priyanka S. and Devi, R. Nandini} } @article {49061, title = {Continuous flow synthesis of mesoporous silica particles with tunable size and structure}, journal = {Industrial and Engineering Chemistry Research}, volume = {63}, year = {2024}, month = {JAN}, pages = {1843-1852}, type = {Article}, abstract = {

We have developed a continuous process to prepare mesoporous silica particles of different sizes and narrow size distribution in a tubular reactor. The method is based on the use of well-known Stober synthesis in the presence of cationic surfactant in methanol-water solvent system and trimethylbenzene as pore swelling agent to form porous silica particles. We observed that reaction parameters had enormous effects on particle size, distribution, and numerous morphological aspects. We demonstrated that these properties may be modified by adjusting the reaction temperature, base concentration, and surfactant concentration. MSPs of spherical morphology with variable size from 400 to 1000 nm produced with the surface area \>600 m(2)/g and pore diameter of 2-4 nm. Large scale production is demonstrated by increasing reactor volume using 1/4 in. PTFE tubing from 20 to 163 mL, with this production of MSPs increased from 0.35 to 3 g/h. The method has been extended for high yield production at the kilogram scale using this approach, which will pave the way toward the industrialization of mesoporous silica based materials.

}, issn = {0888-5885}, doi = {10.1021/acs.iecr.3c03304}, author = {Jundale, Rajashri B. and Prasad, Bhagavatula L. V. and Devi, R. Nandini and Kulkarni, Amol A.} } @article {49180, title = {Deciphering the role of chemisorbed CO in CO2 methanation: kinetic and mechanistic investigation over monometallic (Ru) and bimetallic (Ru-Ni) catalysts}, journal = {Catalysis Science \& Technology}, volume = {14}, year = {2024}, month = {DEC }, pages = {7124-7133}, type = {Article}, abstract = {

Supported metal catalysts have made prominent contributions to CO2 mitigation through conversion into useful chemicals. However, intermediates and mechanisms involved in this process remain ambiguous. Herein, we present the kinetics, mechanistic route and impact of chemisorbed CO in CO2 methanation on Ru/gamma-Al2O3 and Ru-Ni/gamma-Al2O3 catalysts. Both the catalysts show minimal variation in adsorbed species on changing the duration of reduction, as confirmed through in situ IR spectroscopy. A notable observation is that the adsorbed CO exhibits a red shift at a longer reduction time and a more reactive nature on the Ru/gamma-Al2O3 surface. Conversely, stable bridged CO mode is detected on Ru-Ni/gamma-Al2O3 under similar conditions, leading to catalyst poisoning in all instances. This indicates that pre-reduction duration does not have much effect on the surface but interference of CO has more effect at lower concentrations of reactant gases. In situ XRD analysis reveals limited changes in the metallic or mixed oxide species during these conditions. Reaction kinetic analysis showed that Ru-Ni/gamma-Al2O3 has better rate performance at higher concentrations of CO2, whereas Ru/gamma-Al2O3 exhibits better rate performance at lower concentrations. The activation energy was found to be 74.07 kJ per mole for Ru/gamma-Al2O3 and 89.38 kJ per mole for Ru-Ni/gamma-Al2O3. The turnover frequency (TOF) is directly proportional to the rate of formation of methane.

}, issn = {2044-4753}, doi = {10.1039/d4cy01004c}, author = {Dongapure, Pavan and Tekawadia, Jyoti and Naidu, V. Satyam and Devi, R. Nandini} } @article {49182, title = {Environment friendly synthesis of reduced graphene oxide from spent lithium-ion battery graphite and its nanocomposite with MoO3 nanorods for photocatalytic hydrogen evolution}, journal = {Energy \& Fuels}, volume = {38}, year = {2024}, month = {NOV }, pages = {22376-22392}, type = {Article}, abstract = {

Photocatalytic water splitting from solar H2 generation systems is of great interest as a sustainable fuel and an environmentally benign approach. A photocatalyst should be cost-efficient and highly productive to obtain a green H2 fuel. Thus, photocatalytic water splitting is significant for real-world applications. In the present work, we have successfully synthesized MoO3@rGO nanocomposite material with heterojunction as a stable and high-performance photocatalyst for the H2 evolution reaction in deionized (DI) water and natural seawater. First, MoO3 was prepared through a low-temperature hydrothermal method and composites with graphene oxide (GO) and reduced graphene oxide (rGO) precursors, followed by ultrasonication. rGO was obtained from GO, which is obtained from the spent graphite (anode material) by the modified Hummer{\textquoteright}s method. The rGO powder was reduced by an ascorbic acid-reducing agent under microwave irradiation using GO. The nanocomposite materials were characterized using XRD, Raman spectra, XPS, photoluminescence, FE-SEM, HR-TEM, and BET. The photocatalytic water splitting ability of MoO3@rGO was measured under visible light (lambda \>= 420 nm) irradiation with the TEOA sacrificial reagent. The H2 generation rate in DI water and natural seawater was found to be 2183.41 and 2294.26 mu mol g-1 h-1, with an apparent quantum efficiency (AQE) of 5.72 and 5.98\%, respectively. Such a high rate of H2 generated is ascribed to the novel surface contact between MoO3 and the rGO sheet as evident from HR-TEM images, wherein the rGO sheet is seen wrapped around MoO3. Consequently, the synergistic effect between MoO3 and rGO sheets is expected without the use of any other cocatalysts. Thus, electron-hole recombination is significantly minimized during the water reduction reaction. We believe that the MoO3@rGO nanocomposite is a potential photocatalyst for energy production.

}, issn = {0887-0624}, doi = {10.1021/acs.energyfuels.4c03975}, author = {Kangutkar, Raju S. and Walko, Priyanka and Athira, K. and Manjanna, J. and Devi, R. Nandini} } @article {49372, title = {Exploring thermocatalytic pyrolysis to derive sustainable chemical intermediates from plastic waste; role of temperature, catalyst, and reactor conditions}, journal = {Journal of the Indian Institute of Science}, volume = {104}, year = {2024}, month = {APR}, pages = {383-394}, type = {Review}, abstract = {

Plastic waste is a growing concern globally on account of the increasing use of plastic worldwide, compounded by single-use applications, poor waste collection and management practices, and its consequent leakage into the environment. In addition, plastics are derived from non-renewable fossil resources, and their growing demand is also partly responsible for greenhouse gas emissions and climate change. The aim of this paper is to explore the potential of plastic waste as a material resource, and thermocatalytic pyrolysis as a recycling process, to produce aliphatic and aromatic hydrocarbons, which are important chemical intermediates for various industries. We show that plastic pyrolysis can achieve a high yield of liquid hydrocarbons (similar to 80\%) with a suitable distribution of aliphatic and aromatic compounds, by using different pyrolysis conditions and a catalyst. Specifically, this paper demonstrates the possibility of deriving two key classes of hydrocarbons, i.e., aliphatic (C10-C20 hydrocarbons) and aromatic hydrocarbons (xylene, toluene and benzene derivatives) with a yield of similar to 80\% liquid hydrocarbons via catalytic pyrolysis. We also briefly discuss the challenges and opportunities, and the environmental and economic implications.

}, issn = {0970-4140}, doi = {10.1007/s41745-024-00447-3}, author = {Venkataraghavan, R. and Bhure, Arvind and Khan, Tufeil Sartaj and Shikare, Dipak and Devi, R. Nandini and Dhepe, Paresh Laxmikant} } @article {49025, title = {Remarkable SO2 and H2S resistant ability on CO oxidation by unique Pd/WO3 3D hollow sphere nanocatalyst: correlating structure-activity relationships on SO2 exposure}, journal = {ACS Applied Energy Materials}, volume = {7}, year = {2024}, month = {JAN }, pages = {1476-1487}, type = {Article}, abstract = {

We report a simple inorganic route for synthesizing a Pd/WO3 3D hollow sphere nanocatalyst, where Pd nanoparticles are encapsulated and well distributed on porous tungsten oxide nanospheres. The synthesis protocol has advantages, as it requires no surfactant or stabilizing agent, Pd loading is easily tuned, and the as-synthesized nanomaterials can be directly used as catalysts for the CO oxidation reaction. The synthesized nanocatalyst exhibited 100\% CO to CO2 conversion efficiency at 260 degrees C. In addition, the nanocatalyst demonstrated remarkable SO2 (3 ppm) tolerance during the CO oxidation reaction for prolonged SO2 sulfation of 1-21 h at 260-400 degrees C. This represents the longest SO2 exposure time reported to date based on a single metal Pd/support-based nanocatalyst. No decrement in CO conversion efficiency was observed even after SO2 (3 ppm) treatment for 21 h for the first time based on a single metal Pd-based nanocatalyst. Moreover, the synthesized nanocatalyst shows H2S (4 ppm), even in situ H2S tolerance during the CO oxidation reaction at 260 degrees C for 1-3 h and exhibited less sensitivity to prolonged and stringent sulfur exposure, with the highest H2S concentration and maximum 100\% CO to CO2 conversion efficiency obtained after H2S treatment for the first time based on a Pd-based nanocatalyst to the best of our knowledge. The composition and structure of the R-Pd/WO3 nanocatalyst were not much influenced, even after the prolonged SO2 and H2S exposure during the CO oxidation reaction, as verified from spent catalyst analysis. Finally, our DFT-based model provides insights into understanding the observed sulfur resistance on Pd/WO3 by analyzing the underlying electronic structure. Therefore, our strategic synthesis methodology will open up many opportunities to select Pd/metal oxide-based nanomaterials for designing highly efficient, stable, and SO2/H2S-resistant nanocomposite catalyst.

}, keywords = {CO oxidation, DFT calculation, nanocatalyst, palladium (Pd), SO2 andH(2)S resistant ability, structure-activityrelationships, tungstenoxide (WO3)}, issn = {2574-0962}, doi = {10.1021/acsaem.3c02664}, author = {Jeyavani, Vijayakrishnan and Kondhekar, Deepali and Bhati, Meema and Dev, Sahil and Joshi, Kavita and Devi, R. Nandini and Mukherjee, Shatabdi Porel} } @article {49350, title = {Ultra-small Au nanoclusters with tailored photoluminescence properties using modified thiol ligands: a computational and experimental demonstration}, journal = {Particle \& Particle Systems Characterization}, volume = {41}, year = {2024}, month = {OCT}, type = {Article}, abstract = {

Au nanoclusters with tailored photoluminescence can be obtained through controlled nanoparticle ligand interface chemistry. The present work reports molecular gold nanoclusters with tuneable photoluminescence emission from 600 to 700 nm using N,N {\textquoteleft},N {\textquoteleft}{\textquoteright}-trialkyl (11-mercaptoundecyl)ammonium chloride ligands as capping-agents. The tunability within red spectral region is regulated through specific interface chemistry between gold nanoclusters of molecular range and functional groups of the quaternary ammonium head over N,N {\textquoteleft},N {\textquoteleft}{\textquoteright}-trialkyl(11-mercaptoundecyl)ammonium chloride. Combined understanding obtained from the spectroscopy, microscopy, and density functional theory studies demonstrate that the functional group specific electronic interactions at the interfaces steer the emission characteristics of {\textquoteleft}{\textquoteleft}molecular{\textquoteright}{\textquoteright} Au nanoparticles. The study clearly identifies that bulkier functional groups, i.e., triethyl, tripropyl, tributyl, and dimethyl benzene over N+ (of thiol ligand) through their steric effects minimize the particle size giving rise to tunable photoluminescence emission in red spectral region. However, the red shift seen in the emission Au nanoclusters with N-(11-mercaptoundecyl)-N,N {\textquoteleft}-dimethylbenzenammonium chloride ligand in contradiction to particle size effect is computationally proved to be due to the delocalization of electron density from benzene aromatic ring to N+ of ammonium head leading to a reduction in the HOMO-LUMO energy gap. Fluorescence properties of water dispersible Au nanoclusters are tuned by varying the ammonium head group. Density Functional Theory studies correlate the distinction in emission when head group is phenyl to charge transfer characteristics. image

}, keywords = {Density functional theory, photoluminescent Au nanoclusters, surface plasmon resonance, thiol ligand}, issn = {0934-0866}, doi = {10.1002/ppsc.202400011}, author = {Chahande, Anurag M. and Maibam, Ashakiran and Krishnamurty, Sailaja and Devi, R. Nandini} } @article {49771, title = {Coke management: unveiling the role of Ce substitution in Gd2Zr1.8Ni0.2O7-δ catalyst for dry reforming of methane}, journal = {Energy \& Fuels}, volume = {39}, year = {2025}, month = {NOV }, pages = {22356-22368}, type = {Article}, abstract = {

The redox characteristics of cerium have become crucial elements in the carbon gasification process during methane dry reforming. This work examines the effect of cerium substitution in the Gd2Zr1.8Ni0.2O7-delta catalyst during methane dry reforming, employing a range of Ce-substituted Gd2Zr1.8-x Ni0.2Ce x O7-delta (x = 0.1, 0.2, 0.5, 0.75) catalysts synthesized via the citrate gel method. The materials crystallized in a fluorite structure, as verified by X-ray diffraction analysis and Raman spectroscopy. Enhanced reducibility of the substituted catalysts was assessed through H2-temperature-programmed reduction analysis. CO2 and O2 desorption studies along with X-ray photoelectron spectroscopy validated the enhanced basicity and generation of active oxygen and hydroxyl species. The enhanced activity and coke gasification in Gd2Zr1.6Ni0.2Ce0.2O7-delta catalyst are attributed to surface hydroxyl species, and prominent intermediate carbonate and bicarbonate species were further verified by in situ infrared spectroscopy. The high basicity of the Gd2Zr1.6Ni0.2Ce0.2O7-delta catalyst and high concentrations of oxygen vacancies (similar to 66.4\%) enhances CO2 adsorption and desorption, resulting in continuous CO2 activation, leading to less carbon formation and superior activity of the catalyst. The Gd2Zr1.6Ni0.2Ce0.2O7-delta catalyst exhibits the highest CH4 and CO2 conversion rates, at 85\% and 93.5\%, respectively, and remains stable for 100 h. Postreaction analysis of Gd2Zr1.6Ni0.2Ce0.2O7-delta confirms structure stability and less carbon formation compared to other substituted catalysts in dry reforming of methane. This study demonstrates that the moderate concentration of Ce in the Gd2Zr1.6Ni0.2Ce0.2O7-delta catalyst exhibits balanced activity and coke gasification capacity in the dry reforming of methane for a longer duration.

}, issn = {0887-0624}, doi = {10.1021/acs.energyfuels.5c04019}, author = {Ghodke, Seema R. and Mule, Harshada M. and Bhatkar, Akash and Devi, R. Nandini} } @article {49797, title = {Continuous flow hydrodeoxygenation of lignin-derived guaiacol to cyclohexanol over durable Al2O3 hollow fiber supported co catalyst}, journal = {ChemCatChem}, volume = {17}, year = {2025}, month = {SEP}, type = {Article}, abstract = {

The drive to decarbonize the chemical, oil, and gas industries through use of bio-derived resources is intensifying. This study focuses on converting lignin-derived phenolic compounds into cyclohexanol, a precursor for adipic acid production. The alumina hollow fiber supported cobalt catalyst (5Co/AHF@capillary) prepared by capillary action method was found to consist cobalt in both metallic and +delta oxidation states. Initial tests in a batch-mode reactor showed promising results, with 5Co/AHF@capillary catalyst demonstrating catalytic activity comparable to Ru/Al2O3 systems (225 degrees C, 1 MPa H-2, 4 h), achieving similar to 86\% cyclohexanol yield in guaiacol hydrodeoxygenation reactions. The catalytic system was then adapted for continuous flow reactors under milder conditions (300 degrees C, 2.5 MPa H-2, 18 mL min(-1)), resulting in 83\% guaiacol conversion and 74\% cyclohexanol yield. The durability of the catalyst was checked for \>80 h and results claim that catalyst was active in yielding consistent results. The roles of catalyst preparation method, hydrogen pressure, solvent, WHSV were thoroughly checked and discussed.

}, keywords = {biomass valorization, Carbon, Co/Al2O3, Cyclohexanol, lignin}, issn = {1867-3880}, doi = {10.1002/cctc.202500656}, author = {Singh, Dheerendra and Jogdand, Shunottara M. and Devi, R. Nandini and Dhepe, Paresh L.} } @article {49619, title = {Mimicking characteristics of cast iron for enhanced electrocatalytic dehydrogenation of methane}, journal = {Fuel}, volume = {381}, year = {2025}, month = {FEB}, pages = {133674}, type = {Article}, abstract = {

Enhancing the efficiency of methane dehydrogenation through chemical modification of electrocatalytic iron surfaces with impurities that resemble cast iron properties is demonstrated computationally using Density Functional Theory methodologies. Investigating methane dehydrogenation on thermally stable Fe surfaces with discrete planes and anchoring impurities such as Al, C, and Si minimized reduction barriers. Electrochemical treatment of methane on these robust surfaces yields clean hydrogen and carbon-based compounds, such as carbon nanomaterials and carbon black. As for the most efficient active sites for enhanced methane dehydrogenation, the active plane 100 with 5.5 \% C impurities and 0.51 eV reduction barrier is determined to be the most dependable, followed by the active plane 110 with 5.5 \% Si impurities and the lower 0.98 eV reduction barrier. Utilizing CI-NEB (Nudged Elastic Band), the dissociation barrier investigation established the electrolytic catalysts{\textquoteright} performance. This work paves the way for experimentalists and demonstrates the economic viability of Fe-based catalysts for the Catalytic Dehydrogenation of Methane.

}, keywords = {carbon black, Density Functional Theory (DFT), Dry methane reforming (DMR), Electrochemical methane dehydrogenation, Fe surface catalyst}, issn = {0016-2361}, doi = {10.1016/j.fuel.2024.133674}, author = {Verma, Tushar Singh and Devi, R. Nandini and Krishnamurty, Sailaja} } @article {49975, title = {Modulation in surface properties by Ni doping in Na2Ti3O7: effect on dry reforming of methane}, journal = {ACS Applied Engineering Materials}, volume = {3}, year = {2025}, month = {MAY}, pages = {1503{\textendash}1512}, type = {Article}, abstract = {

Dry reforming of CH4\ using CO2\ is considered as an excellent process for converting two greenhouse gases to platform chemicals. However, the challenge is severe coking as well as sintering and consequent deactivation in the absence of steam as in the more prevalent steam reforming. Here, we present a layered Ti-based oxide with appropriate basicity to facilitate CO2\ adsorption and active metal Ni incorporated in the lattice sites to minimize sintering. Ni-doped Na2Ti3O7\ was synthesized using the sol{\textendash}gel method and subsequently characterized and screened in dry reforming of methane. Characterization results indicate the successful formation of the monoclinic phase of Na2Ti3O7. The variant Na2Ni0.2Ti2.8O7, which contains a higher concentration of Ni, exhibited improved reducibility and basicity, as determined through H2-TPR and CO2-TPD analysis. The presence of hydroxide, carbonate, and bicarbonate species was confirmed via X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transformation (DRIFT) studies, leading to increased conversion of CH4\ and CO2\ over extended periods with the Na2Ti2.8Ni0.2O7\ catalyst. Basic Ti{\textendash}OH groups replenished under reaction conditions may play a vital role in reducing coke formation in this catalyst. Post-reaction characterization revealed phase transformations in low Ni content catalysts, as evidenced by X-ray diffraction (XRD) and RAMAN analysis. Additionally, the suppression of coke formation and morphological changes were assessed through thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM) analyses in Na2Ti2.8Ni0.2O7\ catalyst, respectively. The study highlighted the significant influence of elevated Ni concentrations on phase stability and conversion efficiency in the dry reforming of methane. This also evidences the importance of defects created by appropriate doping, which modulates the surface properties facilitating coke gasification.

}, doi = {https://doi.org/10.1021/acsaenm.5c00025}, author = {Ghodke, Seema R. and Devi, R. Nandini} } @article {49880, title = {Understanding the structural characteristics of modified ceramic hollow fiber oxygen transport membranes through in silico tomography simulation study}, journal = {ACS Applied Materials \& Interfaces}, volume = {17}, year = {2025}, month = {JUL }, pages = {43820-43829}, type = {Article}, abstract = {

Design and development of integrated membrane reactor systems are gaining attention as a sustainable solution capable of performing multiple functions in a single reactor. Membrane reactors made of mixed ionic-electronic conduction materials dosing pure O to the reactions can be exploited for various catalytic processes. In this case, micro- and macrostructures of the membrane surface play a significant role in the permeation performance of membranes, and understanding these parameters prior to scaling up to modules is imperative. Here, 3D X-ray tomography imaging, a versatile nondestructive instrumental technique, is used in understanding the structural behavior of the membrane walls at different structural alignments, leading to anticipation of fouling areas upon assembling membrane reactors. La0.6Sr0.4Co0.2Fe0.8O3-delta hollow fiber membranes are fabricated by the phase inversion method and further modified by the optimized acid etching technique. In silico simulations on different morphologies before and after surface modifications are carried out under varying flow rates at nonambient temperatures to mimic real experimental conditions. Critical parameters such as gas velocity, pressure exerted on cavity walls, and strain, dictating structural integrity of the fibers under experimental conditions, were evaluated. As a result of the assessment, the surface-modified structural morphology with finger-like cavities initiating from the inner wall of the membrane was found to be robust. Increase in the pore size, nonuniform pore size distribution, and irregular and interdigitated cavities formed in outer fingered membranes after multiple surface treatments led to an similar to 5 fold increase in the average pressure exerted at the cavity walls when compared to inner fingered membranes. Strain profile generated for inner fingered membranes shows homogeneous distribution of strain for the applied stress throughout the 3D geometry of the membrane. This detailed structural analysis of the membrane will help in building a more robust and efficient system for scale-up applications.

}, keywords = {3D X-ray tomography, in silico simulation, oxygen transport membranes, perovskite, phase inversionmethod}, issn = {1944-8244}, doi = {10.1021/acsami.5c08736}, author = {Jogdand, Shunottara M. and Sharma, Jyoti and Khilari, Rushikesh S. and Mahajan, Digvijay P. and Patil, Prashant and Pol, Harshavardhan V. and Torris, Arun and Agrawal, Ravi and Kharul, Ulhas K. and Devi, R. Nandini} }