The Role of Sulfur-Related Species in Oxygen Reduction Reactions

Heteroatom (metal and nonmetal) doping is essential to achieve excellent oxygen reduc- tion reaction (ORR) activity of carbon materials. Among the heteroatoms that have been studied to date, sulfur (S) doping , including metal sulfides and sulfur atoms, has attracted tremendous attention. Since S-doping can modify spin density distributions around the metal centers as well as the synergistic effect between S and other doped heteroatoms, the S - C bond and metal sulfides can function as important ORR active sites. Furthermore, the S-doped hybrid sample shows a small charge-transfer resistance. Therefore, S-doping contributes to the superior ORR performance. This chapter describes the recent advance-ments of S-doped carbon materials, and their development in the area of ORR with regard to components, structures, and their ORR activities of S-related species.