Au nanoparticle-decorated NiCo^sub 2^O^sub 4^ nanoflower with enhanced electrocatalytic activity toward methanol oxidation

The performance of direct methanol fuel cells hinges on the activity of the catalyst. To enhance the electro-catalytic activity, a flower-like nanostructure assembled from thin Au/NiCo2O4 nanosheet is synthesized via a microwave process combined with deposition-reduction method, where the Au nanoparticles are well dispersed on the surface of the NiCo2O4 nanosheet. The Au/NiCo2O4 composite nanoflower is successfully applied in the electro-catalytic oxidation of methanol and its electro-catalytic performance is investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, which exhibits excellent electro-catalytic qualities towards methanol electro-oxidation in alkaline medium, including low onset potential (0.31 V), high current densities (135.9 mA cm-2 at 0.60 V (vs. SCE), and desirable electro-oxidation stability (94%) after 500 cycles. The activity of NiCo2O4 is significantly enhanced by a small amount of Au for methanol electro-oxidation. Au, a highly electronegative metal, acted as an electron adsorbate, stimulates the generation and stabilization of Co4+ and Ni3+ cations as the active centers for methanol oxidation reactions.