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, Co 9 S 8 embedded in porous nitrogen-doped carbon (N-C) matrix has been designed and fabricated. The as-fabricated Co 9 S 8 /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 Co 9 S 8 /N-C hybrid is superior to that of the RuO 2 /C (20 wt.%), a benchmark electrocatalyst for OER. The stabilities of Co 9 S 8 /N-C hybrid toward ORR and OER are significantly improved as compared to that of Pt/C (20 wt.%) and RuO 2 /C (20 wt.%), respectively. The synergistic effect of the covalent coupling between Co 9 S 8 and N-C and the porous structure of N-C is responsible for the enhanced catalytic activity and durability of Co 9 S 8 /N-C hybrid. [ABSTRACT FROM AUTHOR]