@article {46365, title = {Effect of silicon doping on the reactivity and catalytic activity of gold clusters}, journal = {Journal of Physical Chemistry C}, volume = {118}, year = {2014}, month = {APR }, pages = {7501-7507}, type = {Article}, abstract = {

Doping is known to be an excellent and simple way of catalyst design. Although notable progress has been made in understanding the reactivity and catalytic activity of gas-phase and supported gold clusters, very few studies have been carried out on the doped gold clusters. In the present work, we have carried out density functional theory calculations to investigate the effect of silicon doping on the reactivity and catalytic activity of gold nanoclusters. The present work particularly focuses on the adsorption and activation of molecular oxygen on the pristine and silicon-doped gold clusters. The results confirm that the silicon-doped Au7Si cluster shows considerable binding and activation of the O-2 molecule in comparison to the pristine Au-8 cluster as reflected in the relevant geometrical parameters (O-O and Au-O bond lengths) and O-O stretching frequency. However, silicon doping has no contrasting effect on the reactivity and catalytic activity of the Au-7 cluster. In addition to the stronger binding and activation of the O-2 molecule, the doped Au7Si cluster leads to a significant reduction in the activation barrier (0.57 eV) for the environmentally important CO oxidation reaction in contrast to the catalytically inactive pristine Au-8 cluster (1.22 eV). Thus, our results highlight the critical role of doping foreign impurities for future endeavors in the field of gold nanocatalysis.

}, issn = {1932-7447}, doi = {10.1021/jp501611t}, author = {Manzoor, Dar and Krishnamurty, Sailaja and Pal, Sourav} } @article { ISI:000371608600013, title = {Endohedrally doped gold nanocages: efficient catalysts for O-2 activation and CO oxidation}, journal = {Physical Chemistry Chemical Physics}, volume = {18}, number = {10}, year = {2016}, month = {MAR}, pages = {7068-7074}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Gold nanocages are the most attractive catalytic materials as all the atoms in the cage type clusters reside on the surface, making them available for chemisorption by reacting molecules. Due to a hollow space at the center, their chemical and catalytic properties can be tuned effectively and easily by endohedral doping. While a significant experimental and theoretical understanding is currently available on the structural and electronic properties of doped gold cages, very little information is available on their reactivity and catalytic behavior. In the present work, with the help of density functional theory calculations we demonstrate that endohedral doping leads to a notable increase in the binding energy of molecular oxygen on the gold nanocages. The enhancement in the O-2 binding energy on the doped gold cages is also confirmed by a significant decrease in the Au-O and an increase in the O-O bond lengths, corroborated by a red shift (similar to 250 cm(-1)) in the O-O stretching frequency as compared to the pristine cage. Furthermore, interestingly, the doped gold cages show very low activation barriers for the environmentally important CO oxidation reaction as compared to the pristine gold cage. Importantly, the decrease in the barrier height is comparatively greater for the rate limiting step of O-O-C-O intermediate formation and as a result the CO oxidation is expected to be more facile on the doped gold cages. Thus, the current study highlights the role of heteroatom doping in imparting new chemical and catalytic properties to gold cages and is expected to spur further research in the design of efficient gold nanocatalysts.

}, issn = {1463-9076}, doi = {10.1039/c5cp05624a}, author = {Manzoor, Dar and Krishnamurty, Sailaja and Pal, Sourav} } @article {46126, title = {Effective polysulfide trapping polar interlayer for high rate Li-S batteries}, journal = {Journal of Materials Chemistry A}, volume = {7}, year = {2019}, month = {APR }, pages = {10067-10076}, type = {Article}, abstract = {

A microporous and polymeric C3N4 framework (CNF), when exploited as an interlayer and as a cathode host in Li-S batteries, demonstrates significantly improved electrochemical behavior with a special relevance to high rate applications up to 5C. A CNF obtained through a template free synthesis approach and activated with KOH is endowed with a high specific surface area of 1000 m(2) g(-1), a desirable nitrogen content (13\%) to ensure polarity and a microporous architecture, required to increase the accommodation capability of discharge products. The difference in electronegativity between C and N in CNFs combats in a major way the shuttling of lithium polysulfides (LIPSs) and ensures the realization of increased LIPS binding sites due to the presence of pyridinic nitrogen. Furthermore, a CNF driven change in the molecular configuration of adsorbed LIPSs leads to the uniform distribution and sequestration of discharge products. Similarly, micropores and the polymeric nature of CNFs facilitate the effective confinement of LIPSs and ably accommodate the volume changes (through the formation of Li2S upon discharge) respectively, especially when a microporous CNF interlayer is involved in the Li-S assembly. In particular, a CNF with 60 wt\% sulfur loading, otherwise represented as CNFS-60, when exploited as a cathode in combination with the deployment of a CNF interlayer exhibits appreciable capacity values of 500 and 400 mA h g(-1) at 3 and 5C respectively. Furthermore, the combination of the CNF interlayer and cathode demonstrates a steady state discharge capacity of 437 mA h g(-1) at 1C rate up to 300 cycles, without any significant capacity loss. The involvement of chemical interaction of the CNF with lithium polysulfides is demonstrated using density functional theory calculations. Hence, the effective trapping and the subsequent localization of migrating LIPSs arising from the strong chemical interaction of the CNF with soluble LIPSs and the advantages of high concentration of accessible pyridinic nitrogen sites to the LIPS adsorption in improving the electrochemical behavior of the Li-S system could be understood. This new CNF based interlayer provides a promising approach and ample scope for its implementation in futuristic Li-S batteries.

}, issn = {2050-7488}, doi = {10.1039/c9ta00233b}, author = {Karuppiah, Saravanan and Kalimuthu, Balakumar and Nazrulla, Mohammed Azeezulla and Krishnamurty, Sailaja and Nallathamby, Kalaiselvi} } @article {47774, title = {Electrocatalytic nitrogen reduction directed through the p-band center of boron on BSAC@Mo2C}, journal = {Materials Advances}, year = {2021}, month = {NOV}, type = {Article}, abstract = {Greener modes of ammonia synthesis via the electrocatalytic route have been investigated on pristine and defective Mo2C based monolayers anchored with metal-free boron atom catalysts. Boron single atom catalysts (SACs) on the defective Mo2C monolayer has been found to activate N2 strongly with an adsorption energy of -1.92 eV and reduce it to NH3 efficiently with a significantly low overpotential of 0.41 eV. The exothermic adsorption of N2 and low overpotential for the nitrogen reduction reduction (NRR) appertain to the p-band center of the boron atom catalyst and charge transfer between the adsorbed N2 and the catalyst, respectively. This work brings forth the correlation between electron occupancy on the boron center and NRR catalytic efficiency on a metal-free SACs@Mo2C monolayer couple, thereby serving as a lead in designing metal free electrocatalysts for the NRR.}, doi = {10.1039/D1MA00953B}, author = {Maibam, Ashakiran and Krishnamurty, Sailaja and Dar, Manzoor Ahmad} } @article {47389, title = {Enhanced photocatalytic properties of a chemically modified blue phosphorene}, journal = {RSC Advances }, volume = {11}, year = {2021}, month = {APR }, pages = {13348-13358}, type = {Article}, abstract = {

It is high time to placate the peak demand for an efficient, economic and green fuel in the form of H-2 through photocatalytic water splitting. Several low dimensional materials have been explored for their photocatalytic properties on account of their surface to volume ratio. The present study illustrates the excellent photocatalytic potential of a two-dimensional material, viz. a chemically tempered blue-phosphorene sheet, with single atom thickness and high carrier mobility. Metal-free element, sulphur, is explored as a dopant in a 32-atom blue-phosphorene sheet. The dopant is inserted at three locations viz. central, edge and central edge positions with varying concentrations from 3.125\% to 18.75\% (corresponding to n = 1 to 6 sulphur atoms within a 32-atom blue-phosphorene sheet, P32-nSn). The cohesive energy studies predict the higher stability of even number S doped sheets as compared to their odd counterparts. Photocatalytic activity is studied in terms of band gap and band alignment for different concentrations of the former. Studies reveal that edge doping demonstrates better water molecule activation independent of S atom concentration. The edge doped systems not only provide the chemical activity to activate water, but also show feasible HER overpotentials of 1.24-1.29 eV at neutral medium. Finally, this work opens up a driving lead of non-corrosive catalysts for water molecule splitting.

}, doi = {10.1039/d0ra10829d}, author = {Maibam, Ashakiran and Das, Sawan Kumar and Samal, Pragnya Paramita and Krishnamurty, Sailaja} } @article {47059, title = {Exploring edge functionalised blue phosphorene nanoribbons as novel photocatalysts for water splitting}, journal = {New Journal of Chemistry}, volume = {45}, year = {2021}, month = {FEB}, pages = {3570-3580}, type = {Article}, abstract = {

Hydrogen gas, a highly combustible and eco-friendly fuel is stealing the limelight and its production is one of the major areas of research. An efficient and green method for producing clean hydrogen gas with no harmful by-product is water splitting. With the introduction of low dimensional materials, water splitting has become an easier and cost-effective process. The present work demonstrates the application of one such low dimensional material viz., edge functionalised Blue Phosphorene Nano-Ribbons (BPNRs) as potential photocatalysts. With a carrier mobility of 10(3) cm(2) V-1 s(-1) and a band gap of 1.5-3.0 eV, BPNRs are an attractive candidate for photocatalysis. BPNRs with different edge oreintations, viz. zigzag and armchair are functionalised with CH3O, COOCH3, CHO, COOH, OH, NH2, CONH2, SH, C6H5, and NO2 groups. Their performance towards activating water molecules at different sites on the nanoribbon is studied. The functionalised edges of the BPNRs are the active sites showing similar to 1.2\% to 3.2\% efficiency in activating the O-H bond of the water molecule. Among the different groups explored, CONH2 functionalised zigzag BPNR clearly exhibits a higher potential towards the adsorption of water molecules (-0.98 eV) and activation of O-H bonds with an elongation of 3.2\% and a red shift of 500.6 cm(-1). This is attributed to the lone pair of electrons on the nitrogen atom contributing to the electron donating nature of the CONH2 functional group.

}, issn = {1144-0546}, doi = {10.1039/d0nj03950k}, author = {Maibam, Ashakiran and Chakraborty, Debalina and Joshi, Krati and Krishnamurty, Sailaja} } @article {48327, title = {Electrocatalytic nitrogen reduction on defective graphene modulated from single atom catalyst to aluminium clusters}, journal = {Applied Surface Science}, volume = {623}, year = {2023}, month = {JUN }, pages = {157024}, type = {Article}, abstract = {

Density Functional Theory (DFT) investigation on the most earth-abundant Al-based catalysts, has been conducted detailing its electronic properties and catalytic efficacy for nitrogen reduction at ambient condition. The Al-based catalysts have been modulated to perform as par a highly performing, but rare, Ru-single atom catalytic center by varying number of Al atoms, shape, and size. The coalesce of band-center, work function and electronic properties in metal atom catalysts along with N-N bond activation has been demonstrated to be responsible for an efficient nitrogen reduction reaction (NRR) with Delta Gmax of 0.78 eV in Al5 supported on N-doped double vacancy graphene (Al5@N4-DVG) catalyst. Electron localization function analysis has shown a weak physisorption of N2 in the Al-based catalysts. Projected Density of States (PDOS) illustrates the enhancement of aluminium electron density in Al5@N4-DVG led to enhanced orbital densities overlap of Alp and Np electrons. The Bader charge analysis and electronic analysis of the intermediates show efficient electron gain on the N atoms, leading to formation of NH3 from the NxHy intermediates in Al5@N4-DVG catalyst.

}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2023.157024}, author = {Maibam, Ashakiran and Krishnamurty, Sailaja and BabaRao, Ravichandar} } @article {48445, title = {Expounding lemonal terpenoids as corrosion inhibitors for copper using DFT based calculations}, journal = {Applied Surface Science}, volume = {614}, year = {2023}, month = {MAR}, pages = {156066}, type = {Article}, abstract = {

The most important bottleneck in identifying an innovative and yet viable corrosion inhibitor for copper surfaces is discerning the chemical interactions at the interface of adsorbate and adsorbent. The present work, primarily, discerns the interface chemistry of green corrosion inhibitors, viz., lemonal terpenoids, with the copper surfaces for the first time. The interface chemistry is evaluated for distinct facets of copper, modelled by periodic surfaces to finite sized aggregates, with two stereoisomers viz., citral and neral through density functional calculations. The adsorption/ interaction properties between the surface and the corrosion inhibiting molecule are analysed through the electronic properties such as density of states, charge density difference plots and Bader charges where in distinct bonding mechanisms are identified as a function of varying facets. Apart from the adsorption properties, molecular packing properties are of paramount importance towards the design of an efficient corrosion inhibitor for a surface. Hence, we also analyse the intermolecular stacking energies between the inhibitors when packed among themselves in vacuum and when adhered on to metal surfaces. The studies bring forth an understanding that lemon terpenoids are highly potential corrosion inhibitors for copper surfaces, particularly, for Cu (110) surfaces both in neutral and protonated form.

}, keywords = {Copper surface, Density Functional Theory (DFT), Green corrosion inhibitors, Interface chemistry, Lemonal terpenoids, Molecular stacking}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2022.156066}, author = {Samal, Pragnya Paramita and Singh, Chandrodai Pratap and Krishnamurty, Sailaja} } @article {49516, title = {Effect of cyclization and alkyl group wrapping in visible-light-active unsymmetrical squaraine dyes for dye-sensitized solar cells}, journal = {ACS Applied Energy Materials}, volume = {8}, year = {2025}, month = {APR }, pages = {5017-5030}, type = {Article}, abstract = {

A series of alkyl group-appended indoline- and carboxylic acid-functionalized indolenine-based visible-light-active unsymmetrical squaraine dyes, SQA7-10, were designed, synthesized, and utilized for the dye-sensitized solar cells device fabrication. The number of alkyl group has been increased systematically on the indoline moiety to control the self-assembly of dyes on TiO2 and to passivate the photoanode that helps in improving the open-circuit voltage (V-OC) by avoiding the charge recombination process. SQA7-10 dyes showed an absorption between lambda(max) 536-540 nm, with molar extinction coefficients of 1.62-2.13 x 10(5) M-1 cm(-1) in CH3CN. Further, ultraviolet-visible (UV-vis) studies on TiO2 indicated the formation of H-aggregated dyes (505-510 nm), which can be controlled by appending the alkyl groups. The energy levels of the highest occupied molecular orbital (HOMO) of these dyes are well aligned with the Nernst potentials of I-/I(3)(-)electrolyte and [Cu(tmby)(2)](+/2+) electrolytes with sufficient overpotentials required for the dye regeneration process. DSSC devices made with these dyes showed systematic enhancements of open-circuit voltage (V-OC) and device efficiency with respect to alkyl group incorporation for SQA7-10 with I-/I-3(-) electrolytes. All of the SQA dyes exhibited the device V-OC of more than 805 mV, where the introduction of alkyl groups systematically enhanced the V-OC in the order of SQA7 (805 mV) \< SQA8 (829 mV) \< SQA9 (843 mV) \< SQA10 (862 mV) without any addition of CDCA. Within the SQA dye series, SQA10 dye has achieved the highest DSSC device efficiency of 7.52\% (J(sc) of 11.16 mA/cm(2), V-oc of 862 mV, and ff of 78\%) with I-/I-3(-) electrolyte, whereas use of [Cu(tmby)(2)](+/2+) redox shuttle with SQA10 showed enhanced V-oc (1080 mV) and device efficiency (8.35\%). The IPCE profile for the device fabricated with SQA dyes showed good response at 480 and 560 nm, which indicates the photocurrent generation from the aggregated structures.

}, keywords = {aggregation of dyes, charge recombination, Dye-sensitized solar cells, indoline and indolenine donors, visible-light-activeunsymmetrical squaraine dye}, issn = {2574-0962}, doi = {10.1021/acsaem.4c03116}, author = {Jadhav, Avinash P. and Singh, Ambarish Kumar and Shivankar, Bhavana R. and Siby, Jesna and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} } @article {49506, title = {Effect of doping on electrocatalytic dehydrogenation and hydrogenation of methyl decalin-methyl naphthalene system}, journal = {Journal of Physical Chemistry C}, volume = {129}, year = {2025}, month = {JAN}, pages = {2367-2380}, type = {Article}, abstract = {

The hydrogen economy can benefit from the use of liquid organic hydrogen carriers (LOHCs) for cross-continent hydrogen transportation in the future. However, dehydrogenation and hydrogenation of hydrogen require catalytic systems. Current research emphasizes selective Pt/Rh doping of Fe, Co, and Ni surfaces as catalysts for the dehydrogenation and hydrogenation of the methyl naphthalene-methyl decalin LOHC system, which has more than 7\% hydrogen weight capacity and meets the practical requirements established by the European Union and the United States Department of Energy. Density functional theory-based computational techniques demonstrate how the chemical modification of these surfaces with a Pt and Rh single-atom catalyst (SAC) can improve the efficiency of dehydrogenation and hydrogenation. With a sustainable method, electrochemical dehydrogenation and hydrogenation on these robust surfaces produce effective hydrogen storage for extended periods without losing hydrogen. Furthermore, optimal results for the hydrogenation of 2-methyl naphthalene on Fe-Rh SAC with path-determining step (PDS) = 0.98 eV and dehydrogenation of 1-methyl decalin on Fe-Pt SAC with PDS = 1.49 eV were obtained for the most effective active sites for the enhanced electrochemical process. This study offers new possibilities for the catalytic dehydrogenation and hydrogenation of LOHC systems by highlighting the impact of doping on transition-metal-based catalysts.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.4c07598}, author = {Verma, Tushar Singh and Selvaraj, Kaliaperumal and Krishnamurty, Sailaja} } @article {49491, title = {Evaluating the preferential adsorption of N2 from a binary mixture of N2/O2 on extra-framework cations of zeolites: a computational and experimental study}, journal = {Physical Chemistry Chemical Physics}, volume = {27}, year = {2025}, month = {APR }, pages = {7846-7857}, type = {Article}, abstract = {

Separation of N2 from a N2/O2 gas mixture is critical for various industrial/medical applications. Temperature/pressure swing adsorption is the top-notch industrial technology used for this separation, where zeolites are the materials used for adsorption. Zeolite X/Y with Li+ as an extra-framework cation is the best-known sorbent for N2 gas molecules. However, the present net zero emission scenario has made lithium a critical element, making it imperative to implement its alternative in various other technologies. In this context, the present work is a computational evaluation to identify a cation that can replace Li+ for preferential adsorption of N2 over O2. The DFT study, based on parameters such as selective adsorption energies of N2 over O2 and IR stretching frequencies of the adsorbed N2 and O2 molecules, identifies Mg2+, Ca2+, Sr2+, Co2+ and Zn2+ as potential cations. These cations have preferential adsorption for N2 over O2 by 10 kJ mol-1 or more. However, BOMD simulations reveal that only Mg2+, Ca2+, Co2+ and Zn2+ keep the N2 molecule bound at 300 K and the O2 molecule gets desorbed from these frameworks. The desorption temperature of N2 on Ca2+ and Zn2+ is 350 K and on Mg2+ is 400 K. These observations are corroborated by electronic charges on cations and molecular orbitals. Significantly, Ca2+ is identified to adsorb up to 2 N2 molecules, making it an ideal candidate for N2/O2 separation in place of Li+. To validate this, we have carried out an experimental study that showed a good N2 adsorption capacity of 2.1 mmol g-1 for Ca2+.

}, issn = {1463-9076}, doi = {10.1039/d4cp04193c}, author = {Devasia, George and Nandanwar, Sachin U. and Krishnamurty, Sailaja} }