Strong Co-O-Si bonded ultra-stable single-atom Co/SBA-15 catalyst for selective hydrogenation of CO2 to CO

The design of efficient nonnoble metal catalysts for the hydrogenation of CO 2 is a challenge. Cobalt-based catalysts demonstrate high activity in methanation reactions but low selectivity and stability in reverse water-gas shift reactions. Superstable Co 2+ single atoms supported on SBA-15 with 2.6 wt% Co loading are synthesized by atomic layer deposition. The catalyst performs 99% CO selectivity with a turnover frequency of 304.6 mol CO 2 /mol Co/h at 600°C and stabilizes for 500 h. The performance is ascribed to the strong interaction between Co single atoms and SBA-15 through Co-O-Si bonds that maintain the valence state of Co 2+ during the reaction. Based on DFT and experimental results, a reaction mechanism is proposed involving the dissociative activation of H 2 on single Co atom sites, adsorption of CO 2 , and the formation of CO and H 2 O. The shift between the tetrahedral and the octahedral field of Co 2+ single atoms drives the catalytic cycle. • Ultra-stable Co 2+ single-atom catalyst was synthesized by atomic layer deposition • 99% CO selectivity and near-equilibrium conversion are maintained for 500 h at 600°C • A unique hydrogen-assisted CO 2 direct dissociation mechanism is proposed • Tetrahedral and octahedral field shifting of Co 2+ single atom drives the catalysis The hydrogenation of CO 2 to fuels and chemicals has been recommended as a potential strategy for artificial carbon circulation. The design of efficient nonnoble metal catalysts for CO 2 hydrogenation is a key technology for industrial applications. However, the selectivity and stability of catalysts are limited due to the high reaction temperature. Here, cobalt single-atom catalysts are synthesized and can effectively activate CO 2 and produce CO with a selectivity of 99%. This Co single-atom catalyst is ultra-stable, which can work at 600°C for at least 500 h. An Eley-Rideal-type mechanism of H-assisted dissociation of CO 2 without carbon intermediates is proposed and different from the commonly reported mechanisms. In particular, the CO molecules are generated on the single-atom Co 2+ catalyst via shifting between the tetrahedral field and the octahedral field. Our results provide new insights into designing highly efficient nonnoble catalysts for CO 2 hydrogenation. The single-atom Co/SBA-15 can effectively catalyze CO 2 hydrogenation to CO with high selectivity and stability at 600°C for 500 h. The valence state of Co is maintained at Co 2+ during the reaction, while magnetic moments of Co 2+ shift between 2.59 and 0.94 μ B . The shift between the tetrahedral field and the octahedral field of Co 2+ single atoms contributes to the H-assisted CO 2 dissociation.