Mn 2 V 2 O 7 spiked ball‐like material as bifunctional oxygen catalyst for zinc‐air batteries

Abstract

Hierarchical micro/nanostructures are believed to be magnificent electrocatalyst materials capable of competing with noble metals and the most expensive catalyst materials for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Mn2V2O7-based hierarchical spiked ball structures (MVO SBs) were synthesized using a simple hydrothermal technique as a bifunctional oxygen catalyst for rechargeable Zn-air batteries. The linear sweep voltammetry by a rotating disc electrode was used to investigate the ORR and OER properties and their mechanisms, and the charge transfer mechanism was also studied by electrochemical impedance spectroscopy analysis. When compared with platinum with carbon black (Pt/C), the MVO SB catalyst material exhibited comparable ORR and OER properties. Furthermore, the MVO SB material revealed a 4e− transfer pathway in an electrolyte solution. Furthermore, the prepared MVO SB material demonstrated a lower charge-discharge voltage gap when compared with Pt/C material, which is lower than 180 mV at 45 mA cm−2. The cycling test result of MVO SB catalyst sample revealed excellent cycling stability over 50 charging and discharging cycles (~800 min) than the Pt/C sample (30 cycles [~520 min]). The good catalytic activity and excellent structural stability of the MVO SB material are especially due to the more active sites enhanced by the unique spiked ball-like morphology and high specific surface area (11.70 m2 g−1) properties. The achieved results suggest that the synthesized catalyst material could be employed as an oxygen catalyst material for rechargeable Zn-air batteries.