@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: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: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 {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 {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 {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} }