@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 = {<p>
	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.</p>
},
	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.}
}
@article {48696,
	title = {Co3O4 for sustainable CO2 reduction and possible fine-tuning towards selective CO production},
	journal = {Chemical Engineering Journal},
	volume = {471},
	year = {2023},
	month = {SEP},
	pages = {144459},
	type = {Article},
	abstract = {<p>Two main challenges involved in heterogeneous catalytic CO2 reduction are: (a) decreasing the consumption of H2 to the minimum required level with possibly the maximum CO2 conversion, and (b) concurrently enhancing the selectivity of the desired CO, at the cost of methane. Towards meeting these two challenges, Co3O4 spinel has been identified as a potential catalyst and it exhibits predominant CO selectivity \&gt; 673 K at atmospheric pressure. CO2 conversion begins \&gt; 523 K, with 100\% CO selectivity observed \&gt; 673 K with CO2:H2 = 3:2. Current work shows a sustainable catalytic CO2 conversion to 100\% CO selectivity with Co3O4-Nanocube (NC). Critically, CO selectivity and yield is observed to increase at the cost of methane with smaller amount of H2. 1:1 and 3:2 CO2:H2 ratio exhibits 88-100\% CO selectivity with 24-32.5\% CO2 conversion between 623 and 823 K. Irrespective of the input CO2:H2, ratio of CO2:H2 uptake changes from around 1:3 at 523 K to 1:1-1.5 at 823 K with concurrent production of significant methane to predominant CO, respectively. Surface electronic state changes was explored by near ambient pressure photoelectron spectroscopy, and the results suggests that Co3O4 is the active phase that promotes CO2 reduction selectively to CO. Broadening observed with the vibrational feature of the CO2 molecules at high temperature underscores the heterogeneous character of the catalyst surface, under operating conditions, due to changing electron density. By optimizing the gas hourly space velocity (GHSV), H2-lean CO2:H2 ratio, and the reaction temperature/pressure, 100\% CO selectivity could be broadened to a range of operating conditions.</p>
},
	keywords = {Carbon neutral economy, heterogeneous catalysis, RWGS, SDG, Surface Science},
	issn = {1385-8947},
	doi = {10.1016/j.cej.2023.144459},
	author = {Ranjan, Ravi and Tekawadia, Jyoti and Jain, Ruchi and Mhamane, Nitin B. and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.}
}
