N, P, S Co-Doped Hollow Carbon Supported CuFe Bimetallic Electrocatalysts for Oxygen Reduction in a Wide pH Range

Design of highly active oxygen reduction reaction (ORR) electrocatalysts under a wide pH condition is essential to achieve the versatile application of conversion devices and energy storage. Herein, we utilize the Kirkendall effect to construct an N, P, S co-doped hollow carbon supported CuFe bimetallic catalyst (CuFe/NPS-C). The synergistic effect of CuFe bimetals and the introduction of heteroatoms optimize the adsorption path and regulate the electronic structure, leading to faster ORR kinetics. Additionally, the CuFe/NPS-C catalyst has abundant micropores and mesopores, along with a hollow structure, providing a large specific surface area, which enables the exposure of more catalytic sites, accelerate transport of O₂, and thereby promotes high catalytic activity across a wide pH range. Electrochemical tests show that CuFe/NPS-C exhibits superb catalytic activity at all pH media. Particularly, under neutral conditions, the E_1/2 of CuFe/NPS-C reaches 0.790 V, which is higher than that of most previously reported catalysts and commercial Pt/C. The open-circuit voltages of 1.40 and 1.50 V are respectively presented based on the assembled neutral and alkaline zinc-air batteries (ZABs). Meanwhile, its maximum peak power densities are also greater than those of Pt-based ZABs, reaching 38.9 and 125.9 mW cm^-2, respectively. Besides, CuFe/NPS-C-based batteries achieve charge-discharge durability of 120 h. This study offers novel insights for the design of co-doped bimetallic catalysts, paving the way for efficient ORR electrocatalysts applicable at all pH media.