Density functional theory study of the sulfur/oxygen doped CoN4-graphene electrocatalyst for oxygen reduction reaction

It has been found that hetematoms doped transition metal-nitrogen embedded carbon materials are potential candidates for high-efficient oxygen reduction reaction (ORR) catalysts. Herein, the four-electron ORR mechanism and activity of CoN4, CoN4Sx, and CoN4Ox (x = 1-4) have been investigated theoretically. The results indicate that sulfur (5) doping can effectively enhance ORR activity of CoN4, but oxygen (O) doping cannot. Specifically, due to the weakened *OH binding, the overpotential of CoN4Sx(x = 1-3) is decreased by about 100 mV compared with that of CoN4. Especially, the ORR overpotential of CoN4S1 is as small as 0.25 V. However, for almost all CoN4Ox, the O doping could make the binding strength of *OH be strengthened, leading to high ORR overpotential. The electronic structure analysis of CoN4S1 reveals that due to the activation of nitrogen atoms after S doping and the tuned energy gap of pristine CoN4, its ORR activity is enhanced.

Automated summary

Sulfur (S) doping can effectively enhance the ORR activity of CoN4, while oxygen (O) doping cannot. The overpotential of CoN4S1 is as small as 0.25 V, indicating the beneficial effect of sulfur doping on the catalyst's performance.