Iron Sulfide Nanoparticles Embedded Into a Nitrogen and Sulfur Co-doped Carbon Sphere as a Highly Active Oxygen Reduction Electrocatalyst.

The unique micro/mesoporous spherical nanostructure composed of non-noble metal nanoparticles encapsulated within a heteroatom-doped carbon matrix provides great advantages for constructing advanced non-precious oxygen reduction (ORR) electrocatalysts. Herein, a promising oxygen electrocatalyst comprising iron sulfide (FeS) nanoparticles embedded into a nitrogen and sulfur co-doped carbon sphere (FeS/NS-CS) is successfully explored through a simple and fast polymerization between methylolmelamines (MMA) and ammonium ferric citrate (AFC) as well as a high-temperature vulcanization process. Moreover, the proposed polymerization reaction can be finished completely within a very short time, which is useful for large-scale manufacturing. Impressively, the developed FeS/NS-MCS catalyst demonstrates outstanding ORR catalytic activity in terms of a more positive onset and half-wave potential as well, as much a better methanol tolerance and stability, in comparison with that of Pt/C benchmarked catalyst. The remarkable ORR electrocatalytic properties are strongly associated with the favorable characteristic spherical N, the S co-doped porous graphitic carbon nanoskeleton incorporated with the FeS nanoparticle-encapsulation structure.