MBene promoted Zn peroxide chemistry in rechargeable near-neutral Zn-air batteries

Highly reversible Zn-air batteries (ZABs) in near-neutral aqueous electrolytes can suppress the formation of Zn dendrites and carbonates. However, near-neutral ZABs (NNZABs) based on Zn peroxide (ZnO₂) chemistry are challenging to build due to the air circulation requirement and the Swagelok structure. To achieve cost-effective NNZABs in a coin-cell configuration, it is essential to explore air-breathing cathodes with high catalytic activity for near-neutral systems. Previous studies focused on catalysts for alkaline ZABs, which are usually not suitable for near-neutral batteries. Here, Mo_4/3B_2−xT_z MBene with ordered vacancies is for the first time exploited as a high-performance catalyst for NNZABs. Interestingly, a stable lifecycle for 380 h under a current density of 2 mA cm⁻² and a 5 h cycling period was achieved, which is attributed to the high O₂-adsorbability and air stock capacity of Mo_4/3B_2−xT_z MBene. We also demonstrate that the vacancies at the Y sites of Mo_4/3B_2−xT_z MBene are active sites for boosting the sluggish kinetics of ZnO₂ chemistry. This work highlights the significance of introducing highly efficient cathode catalysts for NNZABs and the high efficiency of MBenes as catalysts in near-neutral systems. © 2023 The Royal Society of Chemistry