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

Abstract

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 g_cat.^-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.