Hydrothermal Synthesis of Highly Dispersed Co3O4 Nanoparticles on Biomass-Derived Nitrogen-Doped Hierarchically Porous Carbon Networks as an Efficient Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions.

Developing high-performance bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of vital importance in energy storage and conversion systems. Herein, we demonstrate a facile hydrothermal synthesis of highly dispersed Co3O4 nanoparticles (NPs) anchored on cattle-bone-derived nitrogen-doped hierarchically porous carbon (NHPC) networks as an efficient ORR/OER bifunctional electrocatalyst. The as-prepared Co3O4/NHPC exhibits a remarkable catalytic activity toward both ORR (outperforming the commercial Pt/C) and OER (comparable with the commercial RuO2 catalyst) in alkaline electrolyte. The superior bifunctional catalytic activity can be ascribed to the large specific surface area (1070 m2 g-1), the well-defined hierarchically porous structure, and the high content of nitrogen doping (4.93 wt %), which synergistically contribute to the homogeneous dispersion of Co3O4 NPs and the enhanced mass transport capability. Moreover, the primary Zn-air battery using the Co3O4/NHPC cathode demonstrates a superior performance with an open-circuit potential of 1.39 V, a specific capacity of 795 mA h gZn-1 (at 2 mA cm-2), and a peak power density of 80 mW cm-2. This work delivers a new insight into the design and synthesis of high-performance bifunctional nonprecious metal electrocatalysts for Zn-air battery and other electrochemical devices.