3D Graphene-Carbon Nanotube Hybrid Supported Coupled Co-MnO Nanoparticles as Highly Efficient Bifunctional Electrocatalyst for Rechargeable Zn-Air Batteries

The development of high-efficiency and low-cost catalysts is one of the core and important issues to improve the efficiency of electrochemical reactions on electrodes, and it is also the goal we ultimately pursue in the commercialization of large-scale clean energy technologies, such as metal-air batteries. Herein, a nitrogen-doped graphene oxide (GO)-carbon nanotube (CNT) hybrid network supported coupled Co/MnO nanoparticles (Co/MnO@N-C) catalyst was prepared with a hydrothermal-pyrolysis method. The unique three-dimensional network structure of substrate allowed for the uniform dispersion of Co-MnO nanoparticles in the carbon skeleton. These characters enable the Co/MnO@N-C to possess the excellent bifunctional electrocatalysts. In alkaline electrolyte, the Co/MnO@N-C presents the outstanding oxygen evolution reaction (OER) performance comparable to the commercial RuO₂ catalyst and the exceedingly good oxygen reduction reaction (ORR) activity with positive half-wave potential of 0.90 V vs. RHE outperforming commercial Pt/C (0.84 V vs. RHE) and the recently reported analogous electrocatalysts. When it is applied to homemade Zn-air batteries, such a non-noble metal electrocatalyst can deliver a better power density, specific capacity and cycling stability than mixed Pt/C and RuO₂ catalyst, and exhibits a wide application prospect and great practical value.