@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 = {

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 \> 673 K at atmospheric pressure. CO2 conversion begins \> 523 K, with 100\% CO selectivity observed \> 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.

}, 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.} } @article {48756, title = {Mechanistic insights into near ambient pressure activity of intermetallic NiZn/TiO2 catalyst for CO2 conversion to methanol}, journal = {ChemCatChem}, volume = {15}, year = {2023}, month = {JAN }, type = {Article}, abstract = {

Ni-Zn pair is predicted through descriptor-based studies to be conducive for CO2 hydrogenation. In this study, NiZn (1 : 1) intermetallics supported on TiO2 is identified as a potential candidate for near ambient pressure activity. The effect of reduction temperature on the catalyst textural properties as well as on CO2 to methanol reduction are explored. Structural and microscopic studies provide clear evidence of phase evolution of NiZn alloy with increasing reduction temperatures, along with phase variations of Zn based oxides. Interface between NiZn intermetallics and ZnO nanoparticles observed at reduction temperature of 550 degrees C, seems to play a crucial role in making this system most active and selective to methanol. In addition, in-situ IR studies provide mechanistic insights and indicates the formation of methanolic species even at ambient pressure.

}, keywords = {CCUS, CO2, In-situ IR, Methanol, near ambient pressure}, issn = {1867-3880}, doi = {10.1002/cctc.202201150}, author = {Dongapure, Pavan and Tekawadia, Jyoti and Thundiyil, Shibin and Caha, Ihsan and Deepak, Francis Leonard and Devi, R. Nandini} } @article {49180, title = {Deciphering the role of chemisorbed CO in CO2 methanation: kinetic and mechanistic investigation over monometallic (Ru) and bimetallic (Ru-Ni) catalysts}, journal = {Catalysis Science \& Technology}, volume = {14}, year = {2024}, month = {DEC }, pages = {7124-7133}, type = {Article}, abstract = {

Supported metal catalysts have made prominent contributions to CO2 mitigation through conversion into useful chemicals. However, intermediates and mechanisms involved in this process remain ambiguous. Herein, we present the kinetics, mechanistic route and impact of chemisorbed CO in CO2 methanation on Ru/gamma-Al2O3 and Ru-Ni/gamma-Al2O3 catalysts. Both the catalysts show minimal variation in adsorbed species on changing the duration of reduction, as confirmed through in situ IR spectroscopy. A notable observation is that the adsorbed CO exhibits a red shift at a longer reduction time and a more reactive nature on the Ru/gamma-Al2O3 surface. Conversely, stable bridged CO mode is detected on Ru-Ni/gamma-Al2O3 under similar conditions, leading to catalyst poisoning in all instances. This indicates that pre-reduction duration does not have much effect on the surface but interference of CO has more effect at lower concentrations of reactant gases. In situ XRD analysis reveals limited changes in the metallic or mixed oxide species during these conditions. Reaction kinetic analysis showed that Ru-Ni/gamma-Al2O3 has better rate performance at higher concentrations of CO2, whereas Ru/gamma-Al2O3 exhibits better rate performance at lower concentrations. The activation energy was found to be 74.07 kJ per mole for Ru/gamma-Al2O3 and 89.38 kJ per mole for Ru-Ni/gamma-Al2O3. The turnover frequency (TOF) is directly proportional to the rate of formation of methane.

}, issn = {2044-4753}, doi = {10.1039/d4cy01004c}, author = {Dongapure, Pavan and Tekawadia, Jyoti and Naidu, V. Satyam and Devi, R. Nandini} }