Engineering Mn–Nx sites on porous carbon via molecular assembly strategy for long-life zinc-air batteries
Zehui Wang, Daijie Deng, Huan Wang, Suqin Wu, Linhua Zhu, Li Xu, Henan Li
Abstract
Nitrogen-coordinated manganese atoms on carbon materials denoted as Mn N C, serve as the highly active non-precious metal electrocatalysts for oxygen reduction reaction (ORR) in zinc-air batteries (ZABs). Nonetheless, a significant challenge arises from the tendency of Mn atoms to aggregate during heat treatment, thereby compromising ORR performance in ZABs. In this work, the molecular assembly strategy based on the hydrogen bond interaction was employed to fabricate the Mn N C electrocatalyst . This approach promotes the dispersion of Mn atoms, creating abundant Mn–N x active sites. Furthermore, the resulting three-dimensional porous nanostructure, formed by molecular assembly, significantly enhances accessibility to the Mn–N x active sites. The porous nanostructure not only shortens the diffusion path of reactants and charges but also improves mass transfer. The Mn N C exhibits impressive ORR catalytic performance with a half-wave potential of 0.90 V (vs. RHE). The liquid-type ZAB based on Mn N C displays a high specific capacity of 816.6 mAh/g and an extended charge–discharge cycle life of 1000 h. Quasi-solid-state ZAB based on Mn N C can operate stably for 24 h. This work presents an effective strategy to synthesize transition metal-nitrogen-carbon (M N C) electrocatalysts tailored for long-life zinc-air battery.