Visible light assisted photo-electrocatalytic oxidation of methanol using low Pt content NiO-rutile TiO2 ternary heterojunction

Platinum decorated binary hetero-junctions of NiO and TiO2 of various mole-ratios have been synthesized for use of these as anode catalysts in the oxidation of methanol in alkali. The as synthesized composites are characterized by X-ray diffraction, spectroscopic and microscopic investigations. The ternary composite having 25.3 mass% of Pt deposited on the binary composite containing 34.36 mass% NiO and 40.34% TiO2 is found to be the best catalyst both in dark and illuminated condition. The peak current density in cyclic voltammetry, the charge transfer conductance, and the steady chronoamperometric current density are increased by about 1.8, 4, and 1.5 times respectively, on the illumination of anode, in comparison to these in the dark. The electrochemical impedance spectroscopy (EIS) and photo responsive current measurements indicate that mixing of NiO with TiO2 demonstrates a superior photo-electm catalytic performance for methanol oxidation plausibly due to enhancement of the electron-hole separation efficiency. Product analysis by HPLC reveals that the formation of formaldehyde, sodium formate, and methyl formate is facilitated on illumination while additional carbonate is formed in the dark.