▎ 摘　　要

Cobalt doped LaMnO3-graphene composites are prepared by sol-gel process assisted with chelating effect of citric acid. The structure, morphology and valence state of samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS). Results show that LaMn1-xCoxO3 particles are homogeneously dispersed on graphene nanosheets, and that doping Co does not change the pervoskite structure. Electrochemical properties are characterized by rotating disk electrode (RDE), rotating ring-disk electrode (RRDE), galvanostatic discharge and AC impedance spectra techniques. The sample prepared with x = 0.1 possesses excellent electrocatalytic activity for oxygen reduction reaction (ORR) and good electrochemical stability in alkaline medium. The measurements of RDE and RRDE reveal that the electron transfer number of LaMn0.9Co0.1O3-graphene is calculated to be 3.87. All the above results indicate that the LaMn1-xCoxO3-graphene composites are promising catalysts with a high catalytic activity toward ORR. (C) 2015 Elsevier Ltd. All rights reserved.