▎ 摘　　要

Cobalt sulfide nanoparticles grown on nitrogen and sulfur dual-doped reduced graphene oxide sheets (CoS/ NS-rGO) were synthesized as an efficient electrocatalyst for the oxygen reduction reaction (ORR) by a facile one-step annealing process at 400-600 degrees C. The catalyst synthesized at 500 degrees C (Co-S/NS-rGO500) exhibits the best ORR catalytic activity compared to the other samples, together with high fourelectron selectivity and excellent stability in alkaline medium. Moreover, the Co-S/NS-rGO-500 composite also manifests good ORR activity and selectivity in acid solution. The facile synthesis approach and superior ORR performance in both alkaline and acid electrolytes make the Co-S/NS-rGO catalysts promising as an alternative to commercial Pt/C catalyst for fuel cells.