Modification of single atomic Fe-N4 catalytic site with sulfur to promote CO2 electroreduction

Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts are one of the more popular materials for electrochemical reduction of CO 2 to fuels and chemicals. Still, their Faraday efficiency and current density are generally low due to the single coordination environment and defect sites. Heteroatom doping has been demonstrated to increase the degree of defects in the material, improve the electron distribution at the single atomic sites, and enhance the catalytic performance. In this study, we prepared an S-doped single-atom catalyst called FeS@PC by a simple high-temperature pyrolysis method for efficient electroreduction of CO 2 to CO, with a maximum CO Faraday efficiency of 97.0% at -0.6 V vs. RHE potential. S atoms doped in the second-shell can change the electron distribution on the Fe-N 4 sites and accelerate the electron transfer during the electrochemical CO 2 reduction reaction (CO 2 RR). Through in situ ATR-FTIR characterization and kinetic experiments, it is found that the doped S can also promote the dissociation of H 2 O, provide sufficient protons for the conversion of CO 2 to *COOH, and promote the rate of CO conversion.