Abstract:

The Mn/N co-doped carbon spheres (Mn@NCS) were synthesized via a dual-template strategy by employing polydopamine (PDA) spheres and Mn-doped ZIF-8 as precursors, which enables precise anchoring of highly dispersed Mn-N_x sites onto the surface of NCS. The introduction of Mn atoms markedly boosts both the catalytic activity of electrochemical oxygen reduction reaction (ORR) and long-term durability, primarily through the synergistic couple between high specific surface area of NCS and hierarchical pore architecture generated by Zn volatilization during pyrolysis. This unique structural configuration effectively optimizes the active-site dispersion and mass-transport efficiency. Electrocatalytic evaluations show that the Mn@NCS achieves an ORR activity with a half-wave potential of 0.84 V (vs. RHE), which is comparable to that of benchmark Pt/C, while maintaining an exceptionally operational durability under extended cycling conditions. When applied as the air-cathode material in zinc-air batteries, the catalyst delivers a superior device performance. Notably, the flow-type battery incorporating Mn@NCS delivers a remarkably operational stability exceeding 160 h, while the flexible battery maintains excellent charge-discharge cycling characteristics under mechanical bending conditions.

Key words: Zinc-air battery, Electrocatalyst, Mn-Nx, Carbon sphere