Effect of different preparation technologies of CuCo2O4 on electrocatalytic activity for oxidation of alcohols

CuCo2O4 for electrocatalytic oxidation of alcohols (methanol, ethanol, ethylene glycol, glycerol) were successfully prepared by coprecipitation method (Cx-CuCo2O4), solvothermal method (Sxy-CuCo2O4) and bimetallic MOF template method (Bxy-CuCo2O4), respectively. The effect of different preparation technologies on the structure, morphology of CuCo2O4 were studied by X-ray diffraction (XRD), scanning electron microscope (SEM). The results show that C4–CuCo2O4 and S44–CuCo2O4 present spherical structure, while B64–CuCo2O4 displays cauliflower strip structure. X-ray photoelectron spectroscopy (XPS) results indicate that the molar ratios of Co3+/Co2+ in C4–CuCo2O4, S44–CuCo2O4 and B64–CuCo2O4 are 1.1, 0.94 and 0.93, respectively, and the area ratio of oxygen vacancy (Ov) to lattice oxygen (Olatt) in C4–CuCo2O4 reaches 0.99 while they are only 0.81 and 0.84 in S44–CuCo2O4 and B64–CuCo2O4 respectively, and more abundant Ov was also detected in C4– CuCo2O4 relative to the spinel oxides obtained by the other two preparation methods via electron paramagnetic resonance (EPR). Furthermore, C4–CuCo2O4 exhibits larger electrochemical active surface area (ECSA), smaller overpotential, lower electrochemical impedance, and smaller Tafel slope, its best catalytic activity may be attributed to its abundant oxygen vacancies and more content of Co3+ on the surface.