MnO2-VO nanorods hybridized with multi-walled carbon nanotubes as an efficient bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

The design and development of cost-effective and highly efficient bifunctional oxygen electrocatalysts hold great significance in the study of metal-air batteries. Herein, the present study describes a facile and scalable strategy for the synthesis of a complex comprising nanorod-like MnO 2 -V O integrated with MWCNTs. For electrochemical performance, MnO 2 -V O /MWCNTs exhibit excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities, demonstrating a half-wave potential ( E 1/2 ) of 0.79 V for ORR and a potential of 1.62 V at 10 mA cm −2 for OER, with a low bifunctional potential difference ( ΔE OER-ORR , between the ORR half-wave potential and the OER potential at 10 mA cm −2 ) of 0.83 V, which are comparable to those of Pt/C and RuO 2 . This excellent catalytic performance can be attributed to the rational design of the MnO 2 -V O components and the unique interwoven network of the MnO 2 -V O /MWCNTs complexes. In addition, the electrocatalytic action and stability improvement mechanisms were also systematically analyzed based on microstructural characterization and electrochemical response. Finally, a zinc-air battery (ZAB) was fabricated by employing the as-synthesized MnO 2 -V O /MWCNTs as the cathode catalyst. The MnO 2 -V O /MWCNTs-based ZAB demonstrates an open-circuit voltage of 1.48 V, a power density of 71.17 mW cm −2 , and superior charge-discharge cycling stability with a voltage gap of only 0.77 V after 100 cycles, which are comparable to those of the commercial Pt/C + RuO 2 -based ZAB (1.39 V, 74.84 mW cm −2 , and 0.87 V gap). This study provides a simple, inexpensive and accessible synthetic method for the design of high-performance non-precious metal-based ORR/OER bifunctional electrocatalysts.