Abstract

A commercially available TiO$\sb2$ powder (Degussa P-25) has been used to prepare thin particulate films on optically transparent SnO$\sb2$ conducting glass electrodes. The oxidation potentials of Resorcinol (RSRCL), 4-Chlororesorcinol (4-CR), 4,6-Dichlororesorcinol (4,6-DCR), Catechol (CC), 3,4-Dihydroxybenzoic acid (3,4-DHBA), and 1,2,4-benzenetriol (1,2,4-THB) in 0.5M KCl were measured. The effect of adsorption on the oxidation potentials of the above-mentioned compounds on TiO$\sb2$ electrodes, were examined by cyclic voltammetry under various conditions. The results show different oxidation potentials vs. SCE for adsorbed versus non-adsorbed species. The scan rate dependencies of the peak currents indicate, that the lower oxidation potential may be assigned to adsorbed reactants while the one at higher potential corresponds to diffusion-controlled oxidation of material from solution. This was also confirmed by the dependence of peak current on the concentration for selected compounds. Illumination causes no significant change in the measured oxidation potentials. However, photocurrent was observed under illumination, indicating the photoactivity of TiO$\sb2.$ These studies tend to indicate that associating the oxidation of such compounds to a single oxidation potential does not adequately describe the situation. Depending on the type of working electrode used, an important distinction is to be made between adsorbed and dissolved species.