N, S co-doped coal-based activated carbon as a high-efficiency and durable metal-free catalyst for the oxygen reduction reaction in Zn–air batteries

Abstract

The development of efficient and stable catalysts for the oxygen reduction reaction (ORR) is crucial to enable practical large-scale application of Zn–air batteries (ZABs). This study investigates the utilization of N, S co-doped coal-based activated carbon materials, synthesized through facile reactions, which exhibit high specific surface area and abundant active sites. The results of material characterization and experiments indicate that co-doping with N and S can effectively modify the charge distribution of coal-based activated carbon materials, increase the active sites, and ultimately enhance their performance in the oxygen reduction reaction (ORR). The N, S-AC catalyst exhibits remarkable catalytic activity for the ORR in alkaline electrolytes, demonstrating a high half-wave potential (E_1/2 = 0.79 V), ultimate current density (j_L = 6.35 mA cm⁻²) and stability, as well as considerable tolerance to methanol. The N, S-AC-based ZAB also demonstrates exceptional performance, achieving a maximum power density of 142 mW cm⁻² and a specific capacity of 804 mA h g_Zn⁻¹. This study not only simplifies the preparation process for heteroatom-doped coal-based activated carbon catalysts but also explores practical applications for ZABs.