TiC-modified α-MnO2 nanowires as highly efficient oxygen electrocatalyst for rechargeable Zn-air batteries

Abstract

One dimensional α-MnO2 nanowires (NWs) have attracted extensive research interests owing to their low cost and excellent activity towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, to date, their application is still limited by insufficient electronic conductivity. The widely applied carbon conductive additives are thermodynamically instable during OER process. Herein, we report for the first time an efficient bifunctional oxygen electrocatalyst for Zn-air batteries (ZABs) based on α-MnO2 NWs modified by stable and highly conductive TiC nanoparticles (NPs). TiC NPs are uniformly distributed on α-MnO2 NWs, which effectively compensate for the relatively low electron conductivity of α-MnO2 NWs and thereby facilitate the charge transfer process. TiC-modified α-MnO2 NWs (TiC/α-MnO2NW) delivers a remarkable bifunctional activity with a half-wave potential of 0.78 V for ORR and a low potential of 1.64 V at 10 mA cm−2 for OER, far exceeding the pristine α-MnO2 NWs. Impressively, its ORR activity is comparable to Pt/C and OER activity is superior to IrO2. The ZAB with TiC/α-MnO2NW achieves a higher peak power density of 161 mW cm−2 and a better cycle performance than those for ZAB using Pt/C–IrO2 benchmark. The TiC/α-MnO2NW material suggests a promising strategy for designing active and durable bifunctional oxygen electrocatalysts.