Graphite photoelectrochemistry - Part 4. Photoelectrochemical studies of quinones in acetonitrile at HOPG electrodes

Stationary photocurrents for reduction of different quinone compounds (benzoquinone, 1,4-naphthoquinone, and 9,10-phenanthroquinone) at irradiated highly oriented pyrolytic graphite (HOPG) electrodes in CH₃CN are reported. Excitation of hot electrons in a graphite electrode by UV-vis light absorption and subsequent hot electron transfer to an acceptor species (quinones) in the electrolyte is assumed to be the source of the photocurrent. This mechanism is supported by photocurrent-potential dependence and photocurrent light action spectra. The effect of the potential drop in the space charge layer of graphite electrodes on photocurrent generation was evaluated by the comparison of photocurrent generation at basal and edge plane HOPG orientations and glassy carbon (GC) electrodes.