Highly mesoporous graphitic catalysts with ternary doping structure towards highly efficient oxygen reduction

Abstract

A new template approach was demonstrated to fabricate Co, N and S co-doped nanoporous graphitic structures for efficiently catalyzing the oxygen reduction reaction (ORR). For preparing such catalysts, a core–shell precursor (FeX@SNDG) was prepared with S and N co-doped graphitic shells by catalytic pyrolysis, and then the S and N co-doped nanoporous graphitic structure was purified by removing ferrous cores with mixed acids. The existence of S-doping could modify the active sites to enhance the catalysis of the ORR, compared with only Co and N co-doped carbonous catalysts. Co-SN-GCs have more positive onset potential (0.97 vs. 0.93 V) and higher kinetic current density (6.2 vs. 5.5 mA cm⁻² at 0.6 V) than Fe-SN-GCs. Density-functional theory calculations indicated that the formation barrier is much lower at Co-SN sites than at Fe-SN sites (0.573 vs. 0.729 eV) in the rate-determining step of the ORR.