Sulfur vacancy-confined Co-Mo sites in MoS2 for high-efficiency CO2 hydrogenation to formate.

CO2 hydrogenation to formate is a significant process for converting greenhouse gas to high-value chemicals. MoS2 catalysts are emerging as low-cost candidates for this reaction, but their performance is constrained by the challenge of generating sufficient and high-activity sulfur vacancy-confined Mo sites as active sites. Here we report that confining Co atoms into MoS2 lattice to substitute Mo atoms (Co-MoS2) remarkably enhances the efficiency of CO2 hydrogenation to formate via enriching sulfur vacancies under practical reaction conditions. The Co-MoS2 achieves a high formate production rate of 17.0 mmol gcat.-1 h-1 with a selectivity exceeding 99% at 200 °C, in which the reaction rate is nearly three times that of the pristine MoS2 catalyst and surpasses previously reported non-precious metal-based catalysts. Experimental characterizations combined with theoretical calculations demonstrate that the weakened bonding between the Co-Mo pair and its adjacent sulfur or oxygen facilitates the removal of sulfur or oxygen for the generation of sulfur vacancies during hydrogenation. The exposed sulfur vacancy-confined Co-Mo sites both at the edge and in the basal plane exhibit moderate CO2 adsorption strength, thus suppressing C-O bond cleavage and promoting selective CO2 hydrogenation to formate.