Iron-Manganese Bimetallic Synergy Boosted Carbon-Based Catalysts for Oxygen Reduction and Zinc-Air Battery Applications

The insufficient intrinsic activity of single-metal active sites severely restricts the further improvement of catalyst performance. Therefore, constructing bimetallic synergistic active sites and regulating the electronic structure of active centers have become effective approaches to break through the performance bottleneck of single-metal M-N-C catalysts. In this study, nitrogen-doped porous carbon sphere supports were prepared using silica as a hard template, and FeMn-N-C bimetallic electrocatalysts were synthesized via an impregnation-reduction method. The oxygen reduction reaction (ORR) catalytic performance of the FeMn-N-C catalyst was systematically compared with that of single-metal Fe-N-C and Mn-N-C catalysts. The results demonstrate that there exists a significant electronic synergistic effect between Fe and Mn bimetals, which can effectively regulate the electronic and geometric structures of active sites and accelerate the kinetic process of the oxygen reduction reaction (ORR). The FeMn-N-C catalyst exhibits excellent ORR performance in alkaline media, with a half-wave potential of 0.878 V and a Tafel slope as low as 49.58 mV·dec⁻¹. The current density can still maintain 91.9% of its initial value after 10000 s. The flexible and aqueous zinc-air batteries assembled with this catalyst as the air cathode achieve peak power densities of 159.4 mW·cm⁻² and 270 mW·cm⁻², respectively, and their comprehensive performance is significantly superior to that of the commercial 40% Pt/C catalyst. This study provides a design strategy for the development of low-cost, high-activity, and high-stability non-noble metal bimetallic ORR electrocatalysts, and broadens their application prospects in zinc-air batteries.