Bimetallic zeolitic imidazole framework-derived sulfur-doped porous carbon as highly efficient catalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Abstract

The oxygen reduction reaction (ORR) is the most sluggish half-reaction in fuel cells; therefore, Pt-group metal (PGM)-based electrocatalysts have been employed to circumvent this limitation. However, the use of Pt, which is a precious metal, significantly limits the commercialization of proton-exchange membrane fuel cell (PEMFC) systems because of the high cost and low durability of Pt-based materials. Herein, we introduce advanced S-doped Co–N–C (CoNC) porous electrocatalysts (S-CoNPCs) derived from zeolitic imidazole frameworks as substitutes for PGM-based electrocatalysts. To improve the electrocatalytic activity of CoNC, sulfur doping, and acid etching treatment methods, which are innovative procedures, are employed to obtain high catalytic activity and a large surface area. S-CoNPC demonstrates an extremely improved electrochemical performance for ORR in both alkaline and acidic mediums compared with commercial Pt/C, exhibiting Eonset, E1/2, and limiting current density of approximately 0.91 V, 0.85 V, and −6.7 mA cm−2 (at 0.40 V vs. RHE), respectively, which are in the suitable range for commercializing the PEMFCs system. Furthermore, S-CoNPC, which exhibits high selectivity, stability, and methanol tolerance, is a promising, novel, and advanced non-PGM electrocatalyst for diverse applications.