Mn³⁺‐rich Manganese Phosphate Targeted for Enhanced Oxygen Reduction Reaction in Zinc‐Air Batteries

Abstract Manganese phosphate‐based materials show great potential in the electrochemical energy field due to the structurally flexible phosphate framework stabilizing active sites. However, the insufficient number of active sites causes unsatisfactory activity. Herein, we prepare Mn₃(PO₄)₂ ⋅ 3H₂O nanosheets via simple liquid‐phase precipitation with hydrogen peroxide as an oxidant, which conduces to expose more Mn³⁺ active sites, thereby accelerating the four‐electron transfer pathway during oxygen reduction reaction. Accordingly, the optimal catalyst (MnPi‐1.0) possesses excellent catalytic performance with a half‐wave potential of 0.81 V and a diffusion‐limited current density of 5.38 mA cm⁻² in contrast to the 0.73 V and 5.07 mA cm⁻² of the pristine one, respectively. Furthermore, the zinc‐air battery based on MnPi‐1.0 delivers a high peak power density (132 mW cm⁻²) and outstanding spcific capacity(797 mAh g_Zn⁻¹). This work provides a facile and feasible solution to tune the density of active sites of manganese phosphate‐based materials for favorable electrochemical performance.