Nickel Oxide Nanoparticles Supported on Graphitized Carbon for Ethanol Oxidation in NaOH Solution

Abstract

NiO nanoparticles were deposited on graphitized carbon support [NiO/G-C] through precipitating nickel hydroxide species followed by calcination at 400 °C. Physicochemical characterization indicated the appearance of two diffraction planes at 2θ values of 43.22° and 62.84° in XRD pattern of NiO/G-C to confirm the nickel oxide species formation. HRTEM image showed a finger print of deposited nanoparticles with lattice fringes distance of 0.152 nm that resembled the lattice distance of NiO(220) plane. The electrocatalytic performance of NiO/G-C electrocatalysts towards oxidizing ethanol molecules was examined in basic solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The oxidation current density of NiO/G-C electrocatalyst was dependent on the loading amount of nickel oxide species. The effect of varying ethanol concentration and scan rate during ethanol oxidation reaction was studied. The reaction order with respect to ethanol concentration was measured in the range of 0.260–0.572 at NiO/G-C electrocatalysts containing variable nickel oxide content. Double-step chronoamperometry was employed to calculate the catalytic rate constant and diffusion coefficient values. They were 8.153 × 102 cm3 mol−1 s−1 and 1.424 × 10−7 cm2 s−1, respectively. A lower charge transfer resistance value was obtained after adding ethanol molecules to NaOH solution confirming the enhanced electrocatalytic activity of NiO/G-C during alcohol oxidation process.