Sulfur doped reduced graphene oxides with enhanced catalytic activity for oxygen reduction via molten salt redox-sulfidation

Abstract

A spontaneous redox reaction of reduced graphene oxide (rGO) in molten Li₂CO₃–Na₂CO₃–K₂CO₃ with a small amount of Li₂SO₄ at 550 °C was applied to synthesize sulfur and sulfur–cobalt doped rGOs (S-rGO/S-Co-rGO). The obtained S-rGOs and S-Co-rGOs show enhanced catalytic activity for the oxygen reduction reaction (ORR) in alkaline aqueous solutions. The onset reduction potential and the half-wave potential of S-Co-rGO are 60 and 40 mV more positive than those of the original rGO, respectively. The reduction current density of S-Co-rGO increases by nearly five times. This study provides a green and continuous molten salt doping approach for the fabrication of heteroatom-doped graphene with excellent catalytic activity for the ORR.