Highly efficient Co−N−C electrocatalysts with a porous structure for the oxygen reduction reaction

Abstract

Developing low-cost, highly-efficient and stable catalysts for the oxygen reduction reaction (ORR) of fuel cells is highly desirable yet challenging. We have developed a Co−N−C ORR catalyst with an intact hollow spherical structure and a large surface area which has been systematically characterized. It was produced by the uniform growth of zeolitic imidazolate frameworks (ZIF s) on the surface of nano-polystyrene (PS) spheres followed by their decomposition. Notably, the as-prepared catalyst Co-NHCP-2 (2 represents a mass ratio of 0.6 between Zn(NO₃)₂·6H₂O and 2-methylimidazole) has a porous structure, a super large specific surface area (1 817.24 m² g⁻¹), high contents of pyridinic-N, pyrrolic-N, and graphitic-N, and a uniform Co distribution. As an efficient electrocatalyst, it shows promise in terms of a high onset potential (E_onset) of 0.96 V, a high half-wave potential (E_1/2) of 0.84 V, and a limited current density of 5.50 mA cm⁻². The catalyst has a nearly 4e pathway for the ORR in an alkaline solution as well as stronger methanol tolerance and higher long-term durability than commercially available Pt/C catalysts. These results show that the obtained material may be a promising electrocatalyst for the ORR.