Photogalvanic effect in aqueous Methylene blue nickel mesh systems: Conversion of light into electricity

The photogalvanic effect in electrochemical cells, employing aqueous Methyl ene blue and Fe(II)/Fe(III) couple electrolyte and nickel-mesh electrodes, were experimentally investigated. Five different standard H-cell configurat ions were set-up by modifying the electrolyte. Long-term open-circuit Volta ge measurements were conducted in order to test the stability of the cells. Light on-off reproducibility experiments were also carried out during leng thy cell operations. By comparing experimental quantum yield with theoretic al predictions, it was found that the cells operate on differential electro de kinetics. Oxidation of the illuminated electrode was detected. This affe cted the current-voltage characteristics of the cells after a sufficiently long cell operation. Schottky junction treatment was used to model the elec trolyte-electrode junction. After calculating the ratio between the majorit y carrier (electron) current density and minority carrier (hole) current de nsity, we concluded that the oxidation of the electrodes contributes positi vely to the cell performance since the electrode-electrolyte interface show s unipolar Schottky diode characteristics. Copyright (C) 2001 John Wiley & Sons, Ltd.