Co9S8-Modified N, S, and P Ternary-Doped 3D Graphene Aerogels as a High-Performance Electrocatalyst for Both the Oxygen Reduction Reaction and Oxygen Evolution Reaction

Efficient and robust electrocatalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play key roles in energy conversion and storage devices. In this work, we construct a bifunctional catalyst by homogeneously dispersing Co 9 S 8 nanoparticles on a nitrogen (N), sulfur (S), and phosphate (P) ternary-doped 3D graphene aerogel (NSPG) matrix via a facile pyrolysis method. Because of the N, S, and P ternary-doping effects, abundant defects and channels are produced in the edge of graphene, resulting in a high specific BET surface area ( S BET ) of 657 m 2 g –1 . With the incorporation of Co 9 S 8 nanocrystals into NSPG, the produced catalyst (Co 9 S 8 /NSPG-900) possesses an S BET of 478 m 2 g –1 with porous characteristics. The synergy of structure and composition features enables fast electrochemical kinetics of the catalyst, leading to efficient ORR activity with a half-wave potential of 0.800 V versus the reversible hydrogen electrode (RHE), a limiting current density of 7.26 mA cm –2, high stability and CH 3 OH tolerance, a high OER performance with an overpotential of 343 mV at the current density of 10 mA cm –2, and excellent long-term stability. As a bifunctional catalyst for both the ORR and OER, it delivers a potential gap of 820 mV, comparable to state-of-the-art bifunctional catalysts.