Preparation of La1−xCaxMnO3 perovskite-graphene composites as oxygen reduction reaction electrocatalyst in alkaline medium

La1−xCaxMnO3 perovskite-graphene composites are synthesized as catalysts for Zn-air cell cathodes. The samples are characterized by thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Results show that perovskite particles are homogeneously dispersed on graphene nanosheets, and that doping Ca does not change the perovskite structure. Electrochemical properties are investigated by galvanostatic discharge, linear sweep voltammetry, and electrochemical impedance spectroscopy techniques. LaMnO3-graphene composites show superior performance than pure LaMnO3. Doping Ca into the composites can tune their catalytic activity and sample prepared with x = 0.4 possesses the highest electrocatalytic activity. The measurement of the rotating ring-disk electrode reveals that the electron transfer number of La0.6Ca0.4MnO3-graphene is 3.6. These results indicate that the La1−xCaxMnO3-graphene composites are potential air electrodes catalysts.