N-doped carbon-coated Co3O4 nanosheet array/carbon cloth for stable rechargeable Zn-air batteries

Although the application of various nonprecious compounds as the air cathodes of Zn-air batteries has been explored, the construction of highly efficient self-supported Co-based electrodes remains challenging and highly desired given their outstanding electrocatalytic activity and cost-effectiveness. Herein, we fabricated a three-dimensional (3D) self-supported electrode based on N-doped, carbon-coated Co3O4 nanosheets grown on carbon cloth (i.e., NC-Co3O4/CC) through electrochemical deposition and carbonization. When used as a binder-free electrode for oxygen evolution reaction (OER), the NC–Co3O4/CC electrode demonstrated excellent electrocatalytic activity with an overpotential of 210 mV at 10 mA cm−2 and a Tafel slope of 79.6 mV dec−1. In the Zn-air battery test, the electrode delivered a small charge/discharge voltage gap (0.87 V at 10 mA cm−2) and exhibited high durability without degradation after 93 cycles at the large current density of 25 mA cm−2. The durability of our electrode was superior to that of a commercial Pt/C+RuO2 catalyst. The excellent performance of NC–Co3O4/CC could be attributed to the presence of 3D structures that promoted electron/ion transfer. By the absence of a binder, the carbon coating improved electron conductivity and promoted electrochemical stability. Moreover, N doping could be used to adjust the C electron structure and aeffective roccelerate electron transfer. The present study provides a facile and ute for the synthesis of various self-supported electrodes that fulfill the requirements of different energy storage and conversion devices.