Cobalt sulfides as efficient catalyst towards oxygen reduction reactions

Abstract

Developing low-cost and high performance catalysts to replace precious metal based catalysts for oxygen reduction reaction (ORR) is one of the most feasible ways to promote the commercial application of fuel cells. In this work, flower-like CoS and octahedral CoS2 are synthesized by a facile one-pot hydrothermal method without any adjunction of surfactants or follow-up thermolysis, their catalytic performance towards ORR in alkaline electrolyte are comparatively investigated. The results reveal that CoS2 outperforms CoS owing to the higher electron density around SS bond of S22- in the crystal structure, which promotes the adsorption of oxygen on catalyst surface and facilitates the breakage of OO bond in oxygen, leading to direct 4-electron transfer ORR. When CoS2 particles are dispersed on the surface of rGO with large surface area, their ORR performance could be further improved.