Reduction of H2O2 at CuInSe2 (Photo)cathodes. I. Characterization of the Electrode-Electrolyte Interface

This study reports electrochemical phenomena observed during reduction of H2O2 at n- and p-CuInSe2 (photo)cathodes in alkaline medium (pH 9 to 10). After cycling the electrode potential in a given potential range, pronounced hysteresis is observed between the two half-cycles of the voltammetry. At both n- and p-materials, during the positive sweep a pronounced increase of the cathodic current is observed at potentials positive of about -0.8 V. In the potential region corresponding to the i/U branch with negative slope, the n- and p-type materials show inverted photocurrents. The photocurrent response is complex showing, e.g., nonproportionality to photon flux and changes in sign. These phenomena are discussed with a qualitative model in terms of changes of the interfacial reactivity caused by the formation of catalytic copper sites on the surface, which kinetically facilitate the process of H2O2 reduction.