Electrochemical and photoelectrochemical studies of copper and cobalt phthalocyanine-tin oxide electrodes

Tetrasulfonated copper and cobalt phthalocyanines have been bound to SnO₂ electrode surfaces modified by either (γ-aminopropyl)triethoxysilane or 3-(N-(2-aminoethyl)aminopropyl)trimethoxysilanes. The electrochemical behavior of the surface bound dye was compared with that of the solution and absorbed forms at SnO₂ in Me₂SO and aqueous media. A stable reversible redox couple was seen on the cobalt phthalocyanine electrodes/SnO₂ in aqueous media. Concentrations of surface bound phthalocyanines were easily detected by monitoring the Cu(2p_1/2,3/2) and N(1s) X-ray photoelectron transitions. SnO₂ electrodes with bound phthalocyanine and SnO₂ electrodes in contact with solutions of phthalocyanines showed similar photoelectrochemical response to the oxidation of oxalate or ascorbate.