Graphite photoelectrochemistry: 2. Photoelectrochemical studies of highly oriented pyrolitic graphite

Alexander D. Modestov, Jenny Gun, Ovadia Lev

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19 Scopus citations


Photoelectrochemical reduction of oxygen and other observations of sustained electrochemically generated photocurrents with graphitic (HOPG) electrodes in aqueous solutions are reported. The photocurrents were observed over a wide pH range: 0 (0.5 M H2SO4)-14 (1 M NaOH). Photocurrent-potential, capacitance-potential and photocurrent light action spectral measurements were performed with basal plane and edge plane HOPG electrodes in order to elucidate the origin of the observed photocurrent. The photocurrent is attributed to hot electron-hot hole pairs photogenerated by direct transition between π-electronic states of the valence and conduction bands of graphite. Photogenerated carriers, holes or electrons, are driven by the electric field in the space charge layer (scl) to the electrode | electrolyte interface, where they react directly with species in the electrolyte inducing anodic or cathodic photocurrent. The potential corresponding to the change of the photocurrent sign from cathodic to anodic was attributed to the flat band potential (EFB). The EFB of the basal plane electrode was 0 V versus SHE regardless of pH, while for the edge plane electrode EFB changed at a rate of 54 mV per unit of pH. The shift of EFB of the edge plane electrode with pH is ascribed to a change of the pH dependent surface dipole formed by oxygen containing surface redox groups.

Original languageAmerican English
Pages (from-to)118-131
Number of pages14
JournalJournal of Electroanalytical Chemistry
Issue number2
StatePublished - 1 Nov 1999


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