Raisin bread-like iron sulfides/nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres: a promising electrocatalyst for the oxygen reduction reaction in alkaline and acidic media†
A raisin bread-like electrocatalyst composed of iron sulfides (Fe1−xS) and nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres (N, S-MGCSs) is successfully synthesized via a two-step pyrolysis and acid leaching process. The resulting Fe1−xS/N, S-MGCS catalysts demonstrate excellent electrocatalytic activities towards the oxygen reduction reaction (ORR) in alkaline and acidic media, the activities of which are closely related to the content and distribution of iron sulfide species. The most optimized electrocatalytic activity achieved over (Fe1−xS/N, S-MGCS)0.2 even outperforms that of the commercial Pt/C catalyst in alkaline media, and is close to that of highly active non-precious metal catalysts reported so far in acidic media. The remarkable catalytic performance is ascribed to the iron sulfide nanocrystals introduced into the highly conductive carbon supports for significantly enhancing the reactivity of catalytically active sites, and the raisin bread-like structure constructed for improving the characteristics of electron and ion transport and inhibiting the self-aggregation and leaching of iron sulfide species. Moreover, this work inspires a new consideration in the field for understanding the catalytic roles of the doped carbon species and transition metal chalcogenides during the ORR electrocatalysis.