Facile synthesis of NiO-modified Mg-doped ZnO thin film electrode for electrocatalytic oxidation of methanol

NiO-modified Mg-doped ZnO composite thin-film electrodes were fabricated on fluorine-doped tin oxide substrates by aerosol-assisted chemical vapour deposition at 400, 500, and 550 °C. The structural, morphological, elemental, and surface chemical properties of the deposited films were investigated using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The film deposited at 550 °C showed the highest crystallinity and the best electrochemical response among the investigated samples. In 0.5 M NaOH containing methanol, this electrode exhibited an apparent onset potential of 0.43 V versus Ag/AgCl and approximately 99% current retention after 2000 s of chronoamperometric testing. Electrochemical impedance spectroscopy showed a decrease in charge-transfer resistance from 627 kΩ in the absence of methanol to 571 kΩ in its presence. These findings demonstrate that the film deposited at 550 °C provides an improved electrochemical response for alkaline methanol electrooxidation under the investigated conditions.