Study on oxygen reduction mechanism of S-doped Fe-NC monatomic catalyst

Heteroatom doped Fe-NC catalyst shows excellent performance in oxygen reduction reaction. In this work, density functional theory was used to study the mechanism of S atom doping on the regulation of electronic structure of Fe-NC monatomic catalyst and the promotion of oxygen reduction reaction. The stable configuration of Fe-NC catalyst after sulfur atom doping, the regulation of electronic structure of fen4 active site by S atom, and the mechanism of oxygen adsorption and oxygen reduction reaction were analyzed. The results show that doping a small amount of S atoms around the fen4 active site can improve the stability of the catalyst. The mechanism of S atom doping to improve oxygen reduction performance is as follows: (1) the doping of S atom reduces the band gap of the catalyst, improves the conductivity of the catalyst, and is conducive to the electrocatalytic oxygen reduction reaction; (2) the doping of S atom can improve the ability of the catalyst to adsorb oxygen, which is conducive to oxygen reduction reaction; (3) the introduction of four S atoms into the system can reduce the overpotential of oxygen reduction reaction and improve the catalytic activity of fen4 site for oxygen reduction reaction. This work may provide a new idea for the regulation of heteroatom doping on carbon-based monatomic catalysts.