01956nas a2200229 4500008004100000022001400041245010000055210006900155260000800224300001200232490000800244520121400252653001201466653000801478653001801486653001601504653002401520100002001544700001901564700001801583856012501601 2019 eng d a0039-602800aNature of electrophilic oxygen: insights from periodic density functional theory investigations0 aNature of electrophilic oxygen insights from periodic density fu cJAN a188-1950 v6793 a

Increasing demand of ethylene oxide and the cost of versatile chemical ethene has been a driving force for understanding mechanism of epoxidation to develop highly selective catalytic process. Direct epoxidation is a proposed mechanism which in theory provides 100% selectivity. A key aspect of this mechanism is an electrophilic oxygen (O-ele) species forming on the Ag surface. In the past two and half decades, large number of theoretical and experimental investigations have tried to elucidate formation of O-ele, on Ag surface with little success. Equipped with this rich literature on Ag-O interactions, we investigate the same using periodic DFT calculations to further understand how silver surface and oxygen interact with each other from a chemical standpoint. Based on energetics, Lowdin charges, topologies and pdos data described in this study, we scrutinize the established notions of O-ele. Our study provides no evidence in support of O-ele, being an atomic species nor a diatomic molecular species. In fact, a triatomic molecular species described in this work bears multiple signatures which are very convincing evidence for considering it as the most sought for electrophilic entity.

10aAg(100)10aDFT10aElectrophilic10aepoxidation10aNucleophilic oxygen1 aKenge, Nivedita1 aPitale, Sameer1 aJoshi, Kavita uhttp://library.ncl.res.in/content/nature-electrophilic-oxygen-insights-periodic-density-functional-theory-investigations02042nas a2200265 4500008004100000022001400041245007100055210006900126260000800195300001100203490000800214520127000222653000801492653000901500653002901509653001201538100001801550700002001568700002001588700002501608700001701633700001301650700001801663856009501681 2020 eng d a0169-433200aMixed metal oxide: a new class of catalyst for methanol activation0 aMixed metal oxide a new class of catalyst for methanol activatio cDEC a1474490 v5343 a

In this work, we propose a mixed metal oxide as a catalyst and demonstrate it's ability to not only activate the MeOH molecule upon adsorption but also dissociate O-H and one of it's C-H bonds. MeOH activation is compared on two prominent facets of ZnAl(2)O(4 )viz. (2 2 0) and (31 1). While spontaneous O-H bond dissociation is observed on both facets, C-H bond dissociates only on the (3 1 1) surface. Multiple factors like atomic arrangement and steps on the surface, coordination of surface atoms, and their effective charges have a combined effect on MeOH activation. The (3 1 1) surface offers higher catalytic activity in comparison with (2 2 0) surface. Having a stepped surface, availability of multiple sites, and variation in the charge distribution are some of the reasons for better catalytic performance of (3 1 1) facet. Effect of orientation of MeOH with respect to the surface adds both, information and complexity to the problem. Observations pertinent to understanding this effect are also reported. A detailed analysis of atomic arrangement on the two surfaces provides a rationale as to why MeOH gets dissociated spontaneously on the mixed metal oxide. The promising results reported here opens up a new class of catalyst for research.

10aDFT10aMeOH10aSpontaneous dissociation10aZnAl2O41 aMehta, Shweta1 aAgarwal, Sheena1 aKenge, Nivedita1 aMekala, Siva, Prasad1 aPatil, Vipul1 aRaja, T.1 aJoshi, Kavita uhttp://library.ncl.res.in/content/mixed-metal-oxide-new-class-catalyst-methanol-activation02063nas a2200205 4500008004100000022001400041245010300055210006900158260000800227300001100235490000800246520139700254653000801651653000901659653002501668653000801693100001801701700001801719856012001737 2022 eng d a0169-433200aFrom molecular adsorption to decomposition of methanol on various ZnO facets: a periodic DFT study0 aFrom molecular adsorption to decomposition of methanol on variou cNOV a1541500 v6023 a

Methanol is an interesting and important molecule to study because of its potential to replace existing fuels. It is also a prominent hydrogen source which can be used to generate hydrogen in-situ. ZnO is widely used as catalyst in synthesis of methanol from CO2 at industrial scale. In this work, we demonstrate that the same catalyst could be used for MeOH decomposition. We have investigated interaction of methanol with various flat and stepped facets of ZnO by employing Density Functional Theory (DFT). Two flat [(10(1)overbar 0) and (11(2)overbar 0)] and two stepped [(10(1)overbar 3) and (11(2)overbar 2)] facets are studied in detail for methanol adsorption. Chemisorption of MeOH with varying strength is common to all four facets. Most importantly spontaneous dissociation of O-H bond of methanol is observed on all facets except (11(2)overbar 0). Our DFT calculations reveal that molecular adsorption is favored on flat facets, while dissociation is favored on step facets. Also, (10(1)overbar 0) facet undergoes substantial reconstruction upon MeOH adsorption. Activation of C-H bond along with strengthening of C-O bond on ZnO facets suggest partial oxidation of methanol. With our DFT investigations, we dig deeper into the underlying electronic structure of various facets of ZnO and provide rationale for the observed facet dependent interaction of ZnO with MeOH.

10aDFT10aMeOH10aSurface interactions10aZnO1 aMehta, Shweta1 aJoshi, Kavita uhttp://library.ncl.res.in/content/molecular-adsorption-decomposition-methanol-various-zno-facets-periodic-dft-study02047nas a2200217 4500008004100000022001400041245010000055210006900155260000800224300001500232490000600247520131900253653002201572653002601594653001401620653000801634653002101642100002001663700001801683856012801701 2022 eng d a2365-654900aLooking beyond adsorption energies to understand interactions at surface using machine learning0 aLooking beyond adsorption energies to understand interactions at cOCT ae2022024140 v73 a

Identifying factors that influence interactions at the surface is still an active area of research. In this work, the importance of analyzing bond length activations (BLact) along with adsorption energies (E-a) while interpreting Density Functional Theory (DFT) results is emphasized. Investigating adsorption of different small molecules, such as O-2, N-2, CO, and CO2, on commonly studied facets ((100), (110), and (111)) of seven fcc transition metal surfaces (M=Ag, Au, Cu, Ir, Rh, Pt, and Pd) demonstrates the missing linear correlation between E-a and BLact. Further, tree based Machine Learning (ML) models reinforce the missing linear correlation between the two parameters and also highlight the importance of analyzing both to develop a better understanding of adsorption at surfaces. The best performing Random Forest models have a mean absolute error (MAE) of 0.19 eV for E-a prediction, and even lower MAE of 0.012 angstrom for BLact prediction. While often d-band center is correlated with E-a, our observations show that infact the d-band center has a better correlation with BLact. These observations emphasizes the role of BLact in gaining a fuller picture for catalysis. The fact that the factors responsible for BLact is a lesser-explored subject adds to the novelty of the findings.

10aAdsorption energy10aBondlength activation10acatalysis10aDFT10amachine learning1 aAgarwal, Sheena1 aJoshi, Kavita uhttp://library.ncl.res.in/content/looking-beyond-adsorption-energies-understand-interactions-surface-using-machine-learning02008nas a2200241 4500008004100000022001400041245006900055210006900124260000800193300001100201490000800212520131900220653001201539653001201551653000801563653001601571653002501587653000801612100001801620700002001638700001801658856009001676 2022 eng d a0039-602800aRole of facet in the competitive pathway of ethylene epoxidation0 aRole of facet in the competitive pathway of ethylene epoxidation cFEB a1219540 v7163 aEthylene epoxide (EtO) is used as raw material for a broad range of products from pharmaceuticals and plastics to paints and adhesives. Although the reaction of ethylene interacting with preadsorbed oxygen on Ag surface is known for decades, the underlying mechanism of EtO formation is not completely understood. Successful investigation of oxametallacycle (OMC) intermediate common to selective as well as non-selective pathways has ensured at least 50% selectivity. The current study brings out the electronic signatures of distinct conformers of OMC stabilised on two different facets of Ag viz. (100) and (111). There are subtle differences between OMC conformers observed on these two facets with near-eclipsed on Ag(100) and near-staggered on Ag(111). A detailed analysis of Ag-O, C-O, C-C, and Ag-C interactions along with projected Density of States (pDOS) and projected Crystal Orbital Hamilton Population (pCOHP) imply towards ring closure on Ag(100) and hydrogen transfer on Ag(111). Finally, our understanding based on electronic and structural signatures are backed up by activation barriers computed through NEB calculations. Activation barrier for EtO is lower on (100) as compared to (111) facet. Thus, our study sheds light on how these differences between OMC affect the selectivity towards EtO.10aAg(100)10aAg(111)10aDFT10aepoxidation10aEthylene Oxide (EtO)10aOMC1 aNair, Aathira1 aKenge, Nivedita1 aJoshi, Kavita uhttp://library.ncl.res.in/content/role-facet-competitive-pathway-ethylene-epoxidation01604nas a2200217 4500008004100000022001400041245009500055210006900150260000800219300001100227490000800238520091100246653000801157653002601165653001301191653002101204653000801225100001801233700001801251856011701269 2023 eng d a0039-602800aElectronic fingerprints for diverse interactions of methanol with various Zn-based systems0 aElectronic fingerprints for diverse interactions of methanol wit cOCT a1223500 v7363 a

We have investigated various Zn-based catalysts for their interaction with methanol (MeOH). MeOH is one of the most critical molecules being studied extensively, and Zn-based catalysts are widely used in many industrially relevant reactions involving MeOH. We note that the same element (Zn and O, in the present study) exhibits different catalytic activity in different environments. The changing environment is captured in the underlying electronic structure of the catalysts. In the present work, we compared the electronic structure of Zn-based systems, i.e., ZnAl2O4 and ZnO along with oxygen preadsorbed Zn (O-Zn) and metallic Zn. We demonstrate the one-to-one correlation between the pDOS of the bare facet and the outcome of that facet's interaction (i.e. either adsorption or dissociation of MeOH) with MeOH. These findings would pave the way towards the in-silico design of catalysts.

10aDFT10aElectronic properties10aMethanol10aZn-based systems10aZnO1 aMehta, Shweta1 aJoshi, Kavita uhttp://library.ncl.res.in/content/electronic-fingerprints-diverse-interactions-methanol-various-zn-based-systems02812nas a2200253 4500008004100000022001400041245008900055210006900144260000800213300001600221490000700237520198700244653000802231653003302239653002302272653001602295653002602311653002802337100002002365700001802385700001802403700001902421856011802440 2023 eng d a0360-319900aHydrogen from catalytic non-thermal plasma-assisted steam methane reforming reaction0 aHydrogen from catalytic nonthermal plasmaassisted steam methane  cJUL a24328-243410 v483 a

Steam methane reforming reaction was carried out in a dielectric barrier plasma reactor. A systematic study is conducted to understand the influence of input power, flow rate, and water for the conversion, yield, and selectivity of the reaction over strategically designed catalysts. In particular, the production rate and selectivity of the products (H2, CO and C2 hydrocarbons) are monitored. CeO2 was used as packing material, mixed with oxides of manganese or copper and their combination. The optimum Cu/CeO2 catalyst illustrated the production rate of 248.7 mmolg-1h-1 and 11.25 mmolg-1h-1 for H2, and CO, respectively at specific energy input of 19.8 JL-1. DFT calculations exhibit apparent change in electronic structure of the CeO2 after inclusion of oxides of manganese and copper that enhance interaction with methane. Based on these findings, a plausible mechanism is elucidatedSteam methane reforming reaction was carried out in a dielectric barrier plasma reactor. A systematic study is conducted to understand the influence of input power, flow rate, and water for the conversion, yield, and selectivity of the reaction over strategically designed catalysts. In particular, the production rate and selectivity of the products (H2, CO and C2 hydrocarbons) are monitored. CeO2 was used as packing material, mixed with oxides of manganese or copper and their combination. The optimum Cu/CeO2 catalyst illustrated the production rate of 248.7 mmolg-1h-1 and 11.25 mmolg-1h-1 for H2, and CO, respectively at specific energy input of 19.8 JL-1. DFT calculations exhibit apparent change in electronic structure of the CeO2 after inclusion of oxides of manganese and copper that enhance interaction with methane. Based on these findings, a plausible mechanism is elucidated which can help to design catalyst for other applications in non-thermal plasma atmosphere. & COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

10aDFT10aDielectric barrier discharge10aNon-thermal plasma10aselectivity10aSpecific energy input10aSteam methane reforming1 aBajpai, Abhinav1 aMehta, Shweta1 aJoshi, Kavita1 aKumar, Sushant uhttp://library.ncl.res.in/content/hydrogen-catalytic-non-thermal-plasma-assisted-steam-methane-reforming-reaction