A hierarchical hybrid ofZnCo2O4andrGOas a significant electrocatalyst for methanol oxidation reaction: Synthesis, characterization, and electrocatalytic performance

Hierarchical porous ZnCo(2)O(4)nanosheets and ZnCo2O4-coated reduced graphene oxide (ZnCo2O4/rGO) were synthesized by the hydrothermal method followed by the annealing process. The composition of materials was proved by X-ray electron spectroscopy and X-ray photoelectron spectroscopy. The size and morphology of the as-prepared samples were evaluated by scanning electron microscopy and transmission electron microscopy. The result showed ZnCo(2)O(4)nanosheets with porous morphology and a sheet thickness of about 5 nm was well synthesized. The electrochemical tests used to prove the catalytic performance of the prepared catalysts were cyclic voltammetry and impedance spectroscopy, and the analysis was performed in alkaline environments. The electrochemical investigations on ZnCo(2)O(4)and ZnCo2O4/rGO showed the rGO has an effective role in electrooxidation of methanol in alkaline media. In addition to the synergic effect between Zn and Co, the synergistic effect between ZnCo2O4(make active sites for adsorption of methanol) and rGO (provide more conductivity and make more sites by preventing from the agglomeration of ZnCo2O4) has an important role for this excellent performance. The polarization curves of ZnCo2O4/rGO showed a maximum power density of 24.3 mW cm(-2), which proved its potential capability for the direct methanol fuel cell.