Electrochemical Fabrication of Porous Ni_0.5Co_0.5Alloy Film and Its Enhanced Electrocatalytic Activity towards Methanol Oxidation

Non-noble Ni 0.5 Co 0.5 alloy with porous micro/nano "holothurian-like" structure is successfully developed via a hydrogen evolution assisted electrodeposition method. The mechanism for the formation of porous Ni 0.5 Co 0.5 alloy structure is analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the hydrogen evolution combined with the anisotropic deposition of Co 2+ account for the formation of this "holothurian-like" structure. The catalytic kinetic studies present that the values of proton diffusion coefficient and surface coverage of the redox species for porous Ni 0.5 Co 0.5 are significantly larger than that of Ni film. Also the reaction rate constant for methanol oxidation at porous Ni 0.5 Co 0.5 alloy is improved by more than one order of magnitude. Finally, the cyclic voltammetry and chronoamperometry tests indicate the Ni 0.5 Co 0.5 electrode has a relatively stable redox behavior after 3000 potential cycles and an improved electrocatalytic stability towards methanol oxidation. The enhanced electrocatalytic activity and stability for porous Ni 0.5 Co 0.5 alloy may be ascribed to the high surface area conducive to the mass transfer process and methanol adsorption and the structural effect of porous micro/nano arrays.