NiO–CoO Hybrid Nanostructures: Preparation, Characterization and Application in Methanol Electro-Oxidation

Abstract

NiO–CoO hybrid nanostructures with improved electrocatalytic activity for methanol oxidation reaction were successfully synthesized via a simple two-step route. Ni/β-Co(OH)₂ precursor was first prepared by a hydrothermal route at 100 °C for 24 h, employing Ni nanospheres, CoSO₄·7H₂O and l-lysine as the reactants; Then, NiO–CoO hybrid nanostructures were obtained by calcining the above precursor in air at 450 °C for 2 h. The as-obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammograms investigations showed that the as-obtained NiO–CoO hybrid nanostructures presented better electrochemical behavior in 1 M KOH solution than single NiO and CoO in the absence/presence of 0.5 M CH₃OH. In the system containing 1 M KOH and 0.5 M CH₃OH, the maximum current densities of various modified electrodes were in turn 175 μA cm⁻² for the NiO–CoO/Ni foam (NF) electrode, 85 μA cm⁻² for the NiO/NF electrode, 80 μA cm⁻² for the CoO/NF electrode and 15 μA cm⁻² for the Ni foam electrode at the potential of 0.6 V. Simultaneously, NiO–CoO hybrid nanostructures still exhibited the lower over-potential and higher stability. The above facts indicated that the as-prepared NiO–CoO hybrid nanostructures were potential candidates as the electrocatalyst for methanol oxidation reaction.