Photoelectrochemical response of methyl viologen cation radical incorporated in coated polysiloxane film

A photoelectrochemical response was found for a methyl viologen pendant polysiloxane film coated on an indium tin oxide (ITO) electrode dipped in an aqueous electrolyte solution containing O₂. Both the current direction (cathodic or anodic) and the extent of the photoresponse depended on the substitutional ratio of methyl viologen on the polymer chain. This behavior was not explained by simple photoinduced electron transfer from the excited cation radical of the methyl viologen to O₂. The mechanism is discussed for steady state O₂ and cation radical concentrations and with respect to O₂ permeability in the polysiloxane film.