TiC supported amorphous MnOx as highly efficient bifunctional electrocatalyst for corrosion resistant oxygen electrode of Zn-air batteries

Abstract

Zn-air batteries (ZABs) represent promising candidates for the next generation energy conversion and storage systems based on their superior features to those of lithium-ion batteries, including high theoretical energy density, low cost, and high safety. However, their further development and application is severely lagged due to the lack of high efficient and durable bifunctional oxygen electrocatalysts. The widely applied carbon-based catalysts are thermodynamically instable during battery charging. Herein, TiC supported amorphous MnOx (a-MnOx/TiC) is reported for the first time as electrocatalyst for the corrosion resistant oxygen electrodes of ZABs. A-MnOx/TiC delivers a remarkable activity and stability toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a high half-wave potential (0.8 V) for ORR and a low potential (1.56 V) at 10 mA cm−2 for OER, which far outperforms the state of the art ORR catalyst (Pt/C) and OER catalyst (IrO2), as well as the Pt/C-IrO2 and a-MnOx/C bifunctional catalysts. The excellent bifunctional activity of a-MnOx/TiC can be attributed to the efficient synergistic effect between the active amorphous MnOx catalyst and the highly conductive and stable TiC support. More impressively, a-MnOx/TiC demonstrates an outstanding electrochemical stability in strong alkaline electrolyte under OER condition in contrast to the readily oxidized carbon-based a-MnOx/C catalysts. ZAB with a-MnOx/TiC delivers a greater discharge performance with a peak power density of 217.1 mW cm−2 than that of Pt/C-based ZAB, and a surpassing discharge and charge cycling performance and stability to ZABs with Pt/C-IrO2 and a-MnOx/C. Furthermore, a-MnOx/TiC can be applied for solid-state ZABs which exhibit excellent mechanical flexibility and cycle stability under their flat and bent states. The a-MnOx/TiC bifunctional electrocatalyst with extraordinarily high activity and electrochemical stability provides a promising approach for exploring corrosion resistant electrocatalysts for Zn-air batteries with high efficiency and long-term cycling stability.