@article { ISI:000349917900007, title = {Can we shift and/or broaden the catalysis regime towards ambient temperature?}, journal = {ChemCatChem}, volume = {7}, number = {4}, year = {2015}, month = {FEB}, pages = {588-594}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

An attempt was made to shift the temperature regime of oxidation catalysis towards ambient temperatures by employing surface modification (SM) as a handle. Systematic SM of Pd(111) was performed by O-atom diffusion into the subsurfaces. Virgin and modified Pd(111) catalysts were evaluated for CO oxidation. Typical CO poisoning observed on virgin surfaces was partially lifted, and ambient CO oxidation was observed on the modified surfaces. CO oxidation was followed by the molecular beam method and near-ambient pressure (NAP) photoelectron spectroscopy under different pressure regimes. UV valence band spectral analysis of the SM and the CO+O-2 reaction on modified Pd(111) surfaces under NAP conditions demonstrated changes in the electronic structures of the surfaces with a change in surface potential by 0.35eV and directly probed CO2 formation under the reaction conditions. Supported metal catalysts may be subjected to SM and evaluated for a shift in the catalysis regime for many different reactions.

}, keywords = {heterogeneous catalysis, Oxidation, photoelectron spectroscopy, surface chemistry, surface modification}, issn = {1867-3880}, doi = {10.1002/cctc.201402979}, author = {Gopinath, Chinnakonda S. and Roy, Kanak and Nagarajan, Sankaranarayanan} } @article { ISI:000354255400032, title = {SBA-15-oxynitrides as a solid-base catalyst: effect of nitridation temperature on catalytic activity}, journal = {Angewandte Chemie-International Edition}, volume = {54}, number = {20}, year = {2015}, month = {MAY}, pages = {5985-5989}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Solid bases, such as SBA-15-oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid-state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.

}, keywords = {heterogeneous catalysis, Nanostructures, NMR spectroscopy, photoelectron spectroscopy, solid-state structures}, issn = {1433-7851}, doi = {10.1002/anie.201501015}, author = {Singh, Baljeet and Mote, Kaustubh R. and Gopinath, Chinnakonda S. and Madhu, Perunthiruthy K. and Polshettiwar, Vivek} } @article {48000, title = {Sustainable CO2 reduction on in (2)O(3 )with exclusive CO selectivity: catalysis and in situ valence band photoelectron spectral investigations}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {10}, year = {2022}, month = {MAR}, pages = {3521-3531}, type = {Article}, abstract = {

This study demonstrates a sustainable catalytic CO2 conversion to near 100\% CO selectivity at ambient pressure on In2O3. Critically, high CO yield could be observed at the cost of undesired methanation, using a lower than stoichiometric amount of hydrogen in the feed; 1:1 and 1:0.67 CO2:H-2 ratios exhibit 98-99.6\% CO selectivity with 25-38\% CO2 conversion between 773 and 873 K. CO2 and H-2 conversion under steady-state conditions at 773-873 K suggests a 1:1 ratio of adsorbed reactants (with 1:0.67 CO2:H-2 feed) on the catalyst surface, underscoring the presence of an ideal reactant composition for the reverse water-gas shift reaction, while H-2-rich feed compositions show the H-2-dominated surface. Surface electronic structure changes, under near-operating conditions, were explored with near ambient pressure photoelectron spectroscopy (NAPPES), and the interesting findings are as follows: (a) A shift in the valence band to lower binding energy, up to 0.6 eV, was observed because of electron filling at high temperatures. (b) An observation of heterogeneous nature of the catalyst surface under NAPPES measurement conditions is attributed to the generation of active oxygen vacancy (O-v) sites, which in turn changes the work function of In2O3. (c) The above changes are found to be reversible, when the reaction was stopped. Vibrational features of the reactant molecules were observed to be broadened in the active temperature window of the catalyst supporting the heterogeneous character of the catalyst surface because of dynamic O-v generation. By optimizing gas hourly space velocity, CO2:H-2 ratio, and reaction temperature, exclusive CO selectivity is possible with a H-2:CO2 ratio of similar to 0.67, which will avoid the product separation stage altogether, while minimizing the expensive H-2 in the reactant feed.

}, keywords = {heterogeneous catalysis, Oxygen vacancy, photoelectron spectroscopy, RWGS, Work function}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c07897}, author = {Mhamane, Nitin B. and Chetry, Sibo and Ranjan, Ravi and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.} }