@conference {45758, title = {Unraveling structure sensitivity in phenol hydrogenaton on Pd nanostructures}, booktitle = {253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes}, year = {2017}, month = {APR }, publisher = {Amer Chemical Soc, 1155 16TH ST, NW, Washington, DC 20036 USA}, organization = {Amer Chemical Soc, 1155 16TH ST, NW, Washington, DC 20036 USA}, address = {San Francisco, CA}, author = {Haider, M. Ali and Seshadri, Sreedhala and Gupta, Shelaka and Khan, Tuhin and Prabhakaran, Vinod} } @article {46320, title = {Mechanistic insights into the pathways of phenol hydrogenation on Pd nanostructures}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {7}, year = {2019}, month = {OCT}, pages = {17126-17136}, type = {Article}, abstract = {

Product selectivity in aqueous phase phenol hydrogenation on well-defined supported Pd nanostructures (spheres, cubes, and octahedra) was studied using defined experiments and density functional theory (DFT) simulations. On Pd spheres and octahedra, the reaction initially showed high selectivity (in the first 3 h, at 363 K and 5 bar H-2 pressure) toward the partially hydrogenated product cyclohexanone. On prolonged operation (\>20 h of reaction time), a shift in the product selectivity (up to 100\%) toward the completely hydrogenated product cyclohexanol was observed on Pd spheres and octahedra. In contrast, the reaction on Pd cubes, which only had {100} facets, showed a high selectivity (similar to 90\%) toward the product cyclohexanone even after 40 h, at the same reaction conditions. Since the {111} facets are expected to be the majority sites on a spherical particle, we attribute the selectivity trend observed on spherical Pd particles to be primarily controlled by the selectivity trend on the Pd{111} facets. This observation was further confirmed on performing the hydrogenation reaction on a mixture of Pd cube and Pd octahedron particles in a ratio of 25:75 (representing the site ratio of a spherical particle). DFT simulations provided a mechanistic insight into the reactivity of the two different facets ({100} and {111}) toward phenol hydrogenation. The calculations revealed that the selectivity significantly depended on the activation barriers involved in cyclohexanone hydrogenation on the Pd{111} facets (77 and 57 kJ/mol) as compared to those on the Pd{100} facets (97 and 101 kJ/mol).

}, keywords = {Cyclohexanol, cyclohexanone, facet-dependent reactivity, phenol hydrogenation}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.9b03392}, author = {Porwa, Govind and Gupta, Shelaka and Sreedhala, S. and Elizabeth, Joes and Ithan, Tuhin Suvra and Haider, M. Ali and Vinod, C. P.} } @article {47746, title = {CuO as a reactive and reusable reagent for the hydrogenation of nitroarenes}, journal = {Applied Catalysis B-Environmental}, volume = {297}, year = {2021}, month = {NOV}, pages = {120417}, type = {Article}, abstract = {{Copper oxide (CuO) is used as a reusable solid reagent for hydrogenation of nitroarenes to aminoarenes. The use of CuO resulted in 100 \% conversion of 2.9 mmol of nitrobenzene to aniline in 45 s at room temperature using hydrazine hydrate as the reducing agent. During the reaction, CuO is converted to inactive metallic Cu which can be regenerated to active CuO by thermal oxidation. DFT simulations indicated facile formation of oxygen vacancies (EO}, keywords = {Copper vacancy, CuO, Hydrogenation, Nitroarene reduction, Oxygen defects, Reactive solids}, issn = {0926-3373}, doi = {10.1016/j.apcatb.2021.120417}, author = {Rajendran, K. and Pandurangan, N. and Vinod, C. P. and Khan, Tuhin S. and Gupta, Shelaka and Haider, M. Ali and Jagadeesan, D.} } @article {47756, title = {Direct oxidation of cyclohexane to adipic acid by a WFeCoO(OH) catalyst: role of bronsted acidity and oxygen vacancies}, journal = {ACS Catalysis}, volume = {11}, year = {2021}, month = {SEP }, pages = {10754-10766}, type = {Article}, abstract = {This work reports the catalytic activity of the trimetallic mixed-metal oxyhydroxide WFeCoO(OH) for the direct oxidation of cyclohexane to adipic acid (AA) without the use of concentrated HNO3. WFeCoO(OH) displayed a 40\% conversion of cyclohexane and a 67\% selectivity to AA under relatively milder conditions of temperature (90 degrees C) and pressure (1 atm). Experimental evidence confirmed the presence of acidic, basic, and redox sites on WFeCoO(OH). The detailed investigation revealed that doping W in the Co-FeO(OH) matrix increased the amount of surface lattice oxygen (OS-L) and caused a significant surge in acidity (5.1 mmol/g). The calculated deprotonation energy of WFeCoO(OH) was 1434 kJ/mol, and the trend in acidity was WCoO(OH) < WFeCoO(OH) < FeCoO(OH) similar to CoO(OH). Energy calculations showed that WFeCoO(OH) had a high propensity to generate oxygen vacancies by the loss of either a water molecule or an oxygen atom (-132.2 or -140.9 kJ/mol, respectively). Basicity was generated due to the presence of conjugate pairs of the surface hydroxyl groups. The combined action of the trifunctional acidic, basic, and redox-active metal centers along with the oxygen vacancies was responsible for the enhanced catalytic performance.}, keywords = {Adipic Acid, deprotonation energy, metal oxyhydroxides, multifunctional catalysts, oxygen vacancies}, issn = {2155-5435}, doi = {10.1021/acscatal.1c01464}, author = {Vernekar, Dnyanesh and Dayyan, Mohammad and Ratha, Satyajit and Rode, V, Chandrashekhar and Haider, M. Ali and Khan, Tuhin Suvra and Jagadeesan, Dinesh} } @article {48200, title = {Unravelling faradaic electrochemical efficiencies over Fe/Co spinel metal oxides using surface spectroscopy and microscopy techniques}, journal = {Nanoscale}, volume = {14}, year = {2022}, month = {NOV }, pages = {15928-15941}, type = {Article}, abstract = {

Cobalt and iron metal-based oxide catalysts play a significant role in energy devices. To unravel some interesting parameters, we have synthesized metal oxides of cobalt and iron (i.e. Fe2O3, Co3O4, Co2FeO4 and CoFe2O4), and measured the effect of the valence band structure, morphology, size and defects in the nanoparticles towards the electrocatalytic hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The compositional variations in the cobalt and iron precursors significantly alter the particle size from 60 to \<10 nm and simultaneously the shape of the particles (cubic and spherical). The Tauc plot obtained from the solution phase ultraviolet (UV) spectra of the nanoparticles showed band gaps of 2.2, 2.3, 2.5 and 2.8 eV for Fe2O3, Co3O4, Co2FeO4 and CoFe2O4, respectively. Further, the valence band structure and work function analysis using ultraviolet photoelectron spectroscopy (UPS) and core level X-ray photoelectron spectroscopy (XPS) analyses provided better structural insight into metal oxide catalysts. In the Co3O4 system, the valence band structure favors the HER and Fe2O3 favors the OER. The composites Co2FeO4 and CoFe2O4 show a significant change in their core level (O 1s, Co 2p and Fe 2p spectra) and valence band structure. Co3O4 shows an overpotential of 370 mV against 416 mV for Fe2O3 at a current density of 2 mA cm(-2) for the HER. Similarly, Fe2O3 shows an overpotential of 410 mV against the 435 mV for Co3O4 at a current density of 10 mA cm(-2) for the OER. However, for the ORR, Co3O4 shows 70 mV improvement in the half-wave potential against Fe2O3. The composites (Co2FeO4 and CoFe2O4) display better performance compared to their respective parent oxide systems (i.e., Co3O4 and Fe2O3, respectively) in terms of the ORR half-wave potential, which can be attributed to the presence of the oxygen vacancies over the surface in these systems. This was further corroborated in density functional theory (DFT) simulations, wherein the oxygen vacancy formation on the surface of CoFe2O4(001) was calculated to be significantly lower (similar to 50 kJ mol(-1)) compared to Co3O4 (001). The band diagram of the nanoparticles constructed from the various spectroscopic measurements with work function and band gap provides in-depth understanding of the electrocatalytic process.

}, issn = {2040-3364}, doi = {10.1039/d2nr04170g}, author = {Kashyap, Varchaswal and Pandikassala, Ajmal and Singla, Gourav and Khan, Tuhin Suvra and Haider, M. Ali and Vinod, C. P. and Kurungot, Sreekumar} } @article {49729, title = {Facet dependence for solvent-modulated proton-coupled electron transfer in furfural acetalization on Pd nanostructures}, journal = {Chemical Engineering Journal}, volume = {514}, year = {2025}, month = {JUN}, pages = {163159}, type = {Article}, abstract = {

Furfural dialkyl acetals prepared via acetalization reaction of furfural and alcohols are promising biofuels. Using defined experiments and density functional theory (DFT) simulations, the structure-dependent activity and selectivity for furfural acetalization reaction in the presence of alcohols (methanol, ethanol, propanol and butanol) as solvents was studied over well-defined supported Pd nanostructures (octahedra (111), cubes (100) and spheres (both (111) and (100)). Pd cubes supported over TiO2 in the presence of ethanol as a solvent (at 303 K and balloon pressure H-2) exhibited 78 \% conversion and 100 \% selectivity for furfural diethyl acetal product in a short time (similar to 180 min). In contrast, Pd octahedra (111) and Pd spheres showed low conversions (18 \% and 6 \%) at the same reaction conditions. Interestingly, when used as a solvent, methanol showed the highest conversion (90 \%) and selectivity (100 \%) for furfural acetalization over Pd cubes. DFT simulations provided mechanistic insight into the reactivity of the two different Pd facets (111) and (100) in the presence of alcohol molecules towards furfural acetalization reaction. A three-step reaction mechanism was proposed for furfural acetalization with alcohols: (i) alcohol hydroxyl-dehydrogenation (ii) hydrogenation of furfural carbonyl oxygen, and (iii) formation of hemiacetal product. For all three steps, Pd (100) exhibited low activation barriers (51.6, 26.7 and 76.2 kJ/mol) compared to Pd (111) surface (78.6, 35.8 and 92.2 kJ/mol) in the presence of ethanol. The activation barriers for the above steps were further reduced to 47.8, 23.9 and 64.6 kJ/mol on Pd (100) in the presence of methanol, explaining the experimental high reactivity aided by methanol. DFT calculations elucidated the role of the hydrogen bonding network between the solvent molecules and adsorbate, enabling proton-coupled electron transfer for accelerated reactions.

}, keywords = {Acetalization, DFT, facet-dependent reactivity, furfural, Furfural dialkyl acetals, solvent effect}, issn = {1385-8947}, doi = {10.1016/j.cej.2025.163159}, author = {Porwal, Govind and Dandekar, Pallavi and Gorai, Twinkle and Khan, Tuhin Suvra and Haider, M. Ali and Gupta, Shelaka and Vinod, C. P.} } @article {50057, title = {Direct conversion of methane to formic acid over Au-Fe-NaZSM-5 at ambient pressure using H2O2}, journal = {Catalysis Science \& Technology}, volume = {16}, year = {2026}, month = {MAR}, pages = {1797-1805}, type = {Article}, abstract = {

Direct conversion of methane to value-added products is a long-standing challenge. This report presents the one-step conversion of methane to oxygenates using H2O2 as an oxidant over an Au and Fe supported on NaZSM-5 (0.1Au0.1FeNZ) catalyst, which produces 4264 mu mol of oxygenates with 89\% selectivity toward formic acid at 10 bar and 60 degrees C within 30 min in a batch process. The catalyst also produces 26.5 mu mol of oxygenates with 70\% selectivity for formic acid at atmospheric pressure and 80 degrees C in a continuous flow process over 9 h of reaction time, making it the first report of such a process. The synergistic interaction of Au and Fe, with the crucial role of Na ions in the zeolite framework in driving the reaction, is revealed through various characterization tools like TEM, XPS, and XAS. Theoretical studies elucidate the active sites responsible for lowering the activation barrier for the crucial C-H activation step. Thus, the catalyst enables the conversion of methane into formic acid with high activity and selectivity, offering new possibilities for harnessing this potent greenhouse gas under process-friendly conditions that were previously unexplored.

}, issn = {2044-4753}, doi = {10.1039/d5cy01422k}, author = {Kumar, Pawan and Ahangar, Iqra and Kesarwani, Srishti and Urkude, Rajashri and Patil, Nita A. R. and Niphadkar, Prashant and Bokade, Vijay V. and Haider, M. Ali and Vinod, C. P.} }