Reversal of Selectivity to CO in CO <sub>2</sub> Hydrogenation by Forming an InCo Alloy and H-ZSM-5 Zeolite-Driven Suppression of Cobalt Oxidation Deactivation in CO <sub>2</sub> Methanation Reaction
Yufeng Li, Jinbiao Yuan, Yu Ji, Siyang Yan, Jiaxu Liu, Bing Liu, Xiaohao Liu
Abstract
Developing efficient and stable catalysts to convert CO 2 to desirable C1 products is of great importance for carbon resource utilization. Cobalt-based catalysts usually show high activity in methanation but poor selectivity to CO from the reverse water-gas shift (RWGS) reaction. Herein, we synthesized In-doped CeO 2 -supported cobalt catalysts for RWGS reaction, which achieved almost reverse 100% selectivity toward CO with a near-equilibrium CO 2 conversion of about 49% at 500 °C and 1 MPa. Results showed that catalyst reduction could result in In species migration onto Co particles to form an InCo alloy, thereby modulating the cobalt electronic structure. It thus strengthened Co–H* bonding but weakened CO adsorption and activation, in turn inhibiting CH 4 formation via HCOO* and CO hydrogenation. Interestingly, the reaction temperature-dependent deactivation was observed over 10Co/CeO 2, owing to cobalt oxidation determined by the O atom chemical potential (μ O ). Theoretical investigations demonstrate that μ O is related to the free energy of H 2 O and H 2 (μ O = G H 2 O ‐ G H 2 ), where the reaction temperature exhibits different degrees of effect on G H 2 O and G H 2 . Based on the deactivation behavior study, we successfully developed a simple strategy to suppress oxidation deactivation by mixing with hydrophilic H-ZSM-5 zeolite to drive H 2 O desorption away from the cobalt surface during the CO 2 methanation reaction with much more H 2 O molecules produced.