Modulating the C and Mo Exposure of Molybdenum Carbide for Efficient Low-Temperature CO2 Reduction to CO

Molybdenum carbides (MoxC) with multiple crystal structures are a group of promising catalysts for low-temperature CO2 reduction to CO. However, the relationship between the C and Mo exposure and the activity is elusive, since control of the C and Mo exposure under the same crystal structures is a difficult task. Herein, the C and Mo exposure at the surface of α-MoC1−x was successfully modulated by control of the S-doped amount in the precursors. It is found that the C exposure was gradually increased with the S doping amount decreasing, and that sole Mo or C exposure will go against CO2 and H2 activation, since bent adsorbed CO2 and H2 dissociation require the synergy of surface C and Mo. In other words, MoC1−x with moderate exposure ratios of C to Mo is most favorable. As a result, the MoC/SiO2-390 catalyst, whose precursor was obtained by annealing molybdenum sulfide at 390 ℃ in air, has the optimal activity, exhibiting a 1001 μmol gcat−1 h−1 of the CO yield with 89