Nano-porous TiO2 electrochemically doped with Mo oxide – Composition, electrochemical and photo-electrochemical properties

Mixed Mo–Ti oxides are synthesized in nano-porous TiO2 templates by electrochemical deposition using cyclic voltammetry and stabilized by thermal treatment. Their thickness, phase, elemental, and chemical composition are characterized using X-ray diffraction, X-ray photoelectron spectroscopy and Glow discharge optical emission spectroscopy. Films are found to contain up to 17%Mo, mainly as Mo(VI) with some amounts of Mo(V). Electrical and electrochemical properties are assessed by current-potential measurements and electrochemical impedance spectroscopy. Photocurrent energy spectra and intensity modulated photocurrent spectroscopy (IMPS) measurements indicate that the films absorb UV and visible light in the range 365–520 nm and exhibit photo-catalytic properties. Quantitative interpretation of IMPS data using a transfer function proposed in the literature yields rate constants of charge transfer and recombination. The dependences of the kinetic parameters on potential are correlated with a mechanistic model of oxygen evolution featuring a mobile intermediate.