The Influence of a Nickel Precursor on the Synthesis of Nanosized NiO Material Using the Hydrothermal Method: Characterization and Electrocatalytic Oxidation of Methanol

Nickel oxide (NiO) was prepared by the hydrothermal method using hydrogen peroxide to form a nickel peroxide complex, and irregular spherical and rod-shaped NiO nanoparticles were obtained. The factors that influence the physical properties of NiO nanoparticles were studied using scanning electron microscopy (SEM), isothermal gas adsorption/desorption by Brunauer, Emmett and Teller (BET), and X-ray diffraction (XRD) techniques. This study found that the precursor salt chosen (nickel acetate or nickel nitrate) significantly affected the shape, particle size, and surface area of the synthesized nanosized NiO powders. The ratio of hydrogen peroxide (H2O2) to nickel nitrate or acetate and the heating rate of calcinations were also important in determining the physical properties of the nanosized NiO. The unmodified PAni electrode shows no activity for the methanol oxidation reaction in 0.1 M NaOH. However, the nickel-modified PAni electrode is a good catalyst for this reaction and high current densities can be reached. The height of the oxidation peak of methanol increases by increasing the alcohol concentration. The results indicate that the reaction of the electro-oxidation of methanol is an activation-controlled proceeding by a direct chemical reaction with NiO(OH) for thin nickel oxides and by charge transfer with the electrode for thick oxides.