Photo-electrochemical reactions of pigmentary titanium dioxide with alcohols and aliphatic amines

Abstract

Addition of methanol, propan-2-ol, benzyl alcohol, polyethylene glycol and polyvinyl alcohol to electrochemical cells having an illuminated electrode consisting of a platinum mesh covered with pigmentary titanium dioxide caused an increase in the anodic photo-current but had little effect on decay of the photo-voltage on termination of illumination. Addition of ascorbic acid reduces the photo-potential and causes a modest increase in photo-current. The photo-currents of the cells are shown to decrease with increase in pH at 0.5 V anodic bias. Addition of aliphatic amines, triethanolamine, dimethylamine and methylamine causes a decrease in photo-voltage and anodic photo-current. When such reactions were carried out with the pH of the electrolyte adjusted to pH 7, enhanced anodic photo-currents were observed and under anodic and cathodic biassing. Oxygen markedly increased the current under cathodic biassing conditions. The results are interpreted in terms of the alcohols and amines being adsorbed on the surface of the pigment and acting as hydrogen atom or electron donors.