Our recent experiments for CO2 methanation reveal that Co catalysts supported on ZrO2 and Al2O3 exhibit good initial activity, but the Co/ZrO2 catalyst is catalytically more active and more stable than the Co/Al2O3 catalyst. Detailed characterization demonstrated that there are notable differences in the adsorption properties of key species between the ZrO2- and Al2O3-supported catalysts and in the metal-support interactions where Co/ZrO2 shows enhanced adsorption for key species and better reducibility of the cobalt oxide. In the present work, we performed density functional theory (DFT) calculations to provide theoretical insight into the support effect over Co/ZrO2 and Co/Al2O3 for CO2 methanation in terms of adsorption and activation of key species. The relative adsorption strengths of CO2, H2, CO, and CH4 species on Co/ZrO2 and Co/Al2O3 calculated by DFT showed qualitative agreement with experimental TPD. Importantly, DFT results uncovered an energetically more favorable H2 dissociative adsorption, faster H* surface migration, and more facile Co-O bond cleavage on Co/ZrO2 than on Co/Al2O3, thus rationalizing the experimentally observed lower temperature and higher degree of cobalt oxide reduction on the ZrO2 support.
All Science Journal Classification (ASJC) codes
- Chemical Engineering (miscellaneous)
- Waste Management and Disposal
- Process Chemistry and Technology