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 CO₂ is a challenge. Cobalt-based catalysts demonstrate high activity in methanation reactions but low selectivity and stability in reverse water-gas shift reactions. Superstable Co²⁺ 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 CO₂/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 Co²⁺ during the reaction. Based on DFT and experimental results, a reaction mechanism is proposed involving the dissociative activation of H₂ on single Co atom sites, adsorption of CO₂, and the formation of CO and H₂O. The shift between the tetrahedral and the octahedral field of Co²⁺ single atoms drives the catalytic cycle.