Cobalt Sulfide Embedded in Porous Nitrogen-doped Carbon as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions

Efficient nonprecious electrocatalysts with fast kinetics for the the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to improve the efficiency of electrochemical systems such as fuel cells and metal-air battereies. Here, Co9S8 embedded in porous nitrogen-doped carbon (N-C) matrix has been designed and fabricated. The as-fabricated Co9S8/N-C hybrid shows an excellent ORR activity, which is comparable to that of the commercial Pt/C (20 wt.%). Notably, the OER activity of Co9S8/N-C hybrid is superior to that of the RuO2/C (20 wt.%), a benchmark electrocatalyst for OER. The stabilities of Co9S8/N-C hybrid toward ORR and OER are significantly improved as compared to that of Pt/C (20 wt.%) and RuO2/C (20 wt.%), respectively. The synergistic effect of the covalent coupling between Co9S8 and N-C and the porous structure of N-C is responsible for the enhanced catalytic activity and durability of Co9S8/N-C hybrid. (C) 2016 Elsevier Ltd. All rights reserved.