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

Abstract

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.