▎ 摘　　要

Urea was used as the nitrogen source precursor, nitrogen-doped reduced graphene oxide was prepared by thermal annealing, and then nitrogen-doped reduced graphene oxide/tri-cobalt-doped hybrid nanosheet was prepared by hydrothermal method using cobalt acetylacetonate as cobalt source. Reduction and oxygen evolution of the bifunctional catalyst. Firstly, the microstructures were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The catalysts were found to have a unique layered mesoporous structure. The formation of spinel tetraoxide with spinel structure in the catalyst was verified by X-ray electron spectrometer (XPS) and X-ray diffractometer (XRD). Thermogravimetric analysis indicated that the content of nitrogen-doped graphene and tricobalt tetroxide in the catalyst was 68.43% and 31.57%(w/w), respectively. Electrochemical tests such as rotating disk electrodes showed that the catalyst exhibited superior oxygen reduction and oxygen evolution catalytic properties. In an alkaline environment, the initial potential, half-wave potential, and limiting current density were 1.171 V, 0.718 V, and 4.3 mA.cm(-2), respectively. The Koutecky-Levich equation shows that the catalyst directly reduces oxygen by a four-electron process. In water, the catalytic efficiency was high. The oxygen evolution catalytic performance test showed that the overpotential at the current density of 10 mA.cm(-2) was 1.789 V, and the Tafel slope was 134 mV.dec(-1), which had good oxygen evolution kinetics. The difference of overpotential (Delta E) was 1.071 V, which was superior to common dual-function catalysts.