Graphite photoelectrochemistry study of glassy carbon, carbon-fiber and carbon-black electrodes in aqueous electrolytes by photocurrent response

Photocurrent generation by UV-vis light irradiation of glassy carbon, boronated glassy carbon, carbon-black and carbon-fiber electrodes was studied in comparison with the behavior of HOPG basal plane and edge plane electrodes. The presence of a space charge layer at these electrodes was manifested by photogeneration of electrochemical currents. Both anodic and cathodic photocurrents were observed for all the forms of graphitic materials investigated. An exponential dependence of photocurrent magnitude on electrode potential and on photon energy was found for all the forms of graphitic materials. The exponential response was explained by a model involving the generation of a hot charge carrier by photoexcitation in the space charge layer, transport to the solid-electrolyte interface and subsequent interfacial charge transfer reactions. Studies of photocurrent-potential dependence performed with glassy carbon, boronated glassy carbon and carbon-black electrodes in highly acidic to highly basic aqueous solutions (pH 0-14) revealed a linear dependence of the flat bands potential on pH with a slope of approximately 0.05 V per unit of pH.