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

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.