Application of phosphotungstic acid–nickel composite-modified carbon paste electrode for electrocatalytic oxidation of methanol in alkaline solution

Phosphotungstic acid (PWA) was used for accumulation of nickel ions at the carbon paste electrode for preparation of PWA-modified CPE (PWA/CPE). The PWA was evenly mixed with graphite powder and paraffin oil. Then, for preparation of Ni/PWA/CPE, Ni ions were included onto the PWA/CPE surface through immersion method at open circuit condition. The scanning electron microscopy (SEM), energy-dispersive spectroscopy and electrochemical methods were used to verify the prepared electrodes. The SEM images reveal that morphology of the CPE was influenced by PWA addition. Application of the Ni/PWA/CPE for methanol oxidation was explored by various electrochemical techniques. Electrochemical response of methanol oxidation at the surface of Ni/PWA/CPE was 2.5 times higher than that Ni/CPE. The obtained results indicated that the modified electrode exhibited high electrocatalytic activity toward methanol oxidation. Then, catalytic rate constant was found to be 8.25 × 104 cm3 mol −1 s−1 using chronoamperometry method. Furthermore, the effects of several parameters, such as PWA loading, NiSO4 concentration, accumulation time and methanol concentration toward methanol oxidation at the surface of this modified electrode as well as stability, have been investigated.