A strategy for fabricating three-dimensional porous architecture comprising metal oxides/CNT as highly active and durable bifunctional oxygen electrocatalysts and their application in rechargeable Zn-air batteries

Abstract

Approaches to structural and compositional modifications of non-noble metal oxygen reduction reaction and oxygen evolution reaction electrocatalysts are essential for advanced rechargeable Zn-air batteries (ZABs). In this work, three-dimensional (3D) porous carbon nanotube (CNT) microsphere prepared by spray pyrolysis are used as conductive carbon framework. MnO2 and Fe2O3 nanorods are uniformly deposited on rationally designed CNT microsphere via a two-step bottom-up processing; through the formation of 3D porous architecture, electron transfer and mass transport can be facilitated. Due to the synergetic effect of uniformly deposited MnO2 and Fe2O3 nanorods and 3D porous architecture of CNT framework, MnO2-Fe2O3/CNT exhibited superior oxygen reduction/evolution catalytic activities under alkaline media comparing to Pt/C-RuO2. Moreover, as a bifunctional electrocatalyst for ZABs, MnO2-Fe2O3/CNT delivered high power density of 253 mW cm−2, specific capacity of 802 mA h g−1, and low polarization potential difference, as well as long-term cycling stability up to 3600 min.