Investigations on the Photoprotection Ability of TiO₂ Coated on Copper

A TiO2 coating when directly applied on copper plate showed an instantaneous ptype behavior, i.e. ennoblement of electrode potential on ultraviolet (UV) illumination though a copper plate when galvanically coupled to an ITO glass coated with TiO2 showed immediate lowering of electrode potential (‘n’-type effect) on illumination under deaerated conditions. The instantaneous p-type effect in the former case was attributed to the presence of a copper oxide layer present between the copper plate and the TiO2 coating. However, a prolonged exposure of the TiO2 coated copper plate showed an n-type effect under illumination after nearly 24 h, following which the electrode potential appeared stable and highly negative. This observation indicated that the photogenerated electrons in TiO2 are capable of reducing the copper oxide layer to ultimately realize the n-type effect of TiO2. The n-type effect could not be observed in aerated electrolyte solutions. The effect of different conditions in the ambience on the photoeffect of copper coated TiO2 will be discussed.