Abstract

The effect of different hole accepters on the photocurrent response of particulate TiO2 anodes was investigated. In all cases there was a significant increase in the photocurrent over that observed for the photoooxidation of water. The photocurrent efficiency observed in the presence of hole accepters followed the order: oxalate > formate > acetate > methanol. The order of efficiency of the hole accepters does not correlate with reported free hydroxyl radical reactivity constants or with reported oxidation potentials for the substrates studied. Adsorption measurements made in the dark showed that oxalate was much more strongly adsorbed on the electrode surface than either acetate or formate. Impedance spectroscopy indicated an increase in the capacitance of the system due to the presence of oxalate, both in the dark and under illumination.