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

The photogalvanic effect in electrochemical cells, employing aqueous Methylene blue and Fe(II)/Fe(III) couple electrolyte and nickel-mesh electrodes, were experimentally investigated. Five different standard H-cell configurations were set-up by modifying the electrolyte. Long-term open-circuit Voltage measurements were conducted in order to test the stability of the cells. Light on-off reproducibility experiments were also carried out during lengthy cell operations. By comparing experimental quantum yield with theoretical predictions, it was found that the cells operate on differential electrode kinetics. Oxidation of the illuminated electrode was detected. This affected the current-voltage characteristics of the cells after a sufficiently long cell operation. Schottky junction treatment was used to model the electrolyte-electrode junction. After calculating the ratio between the majority carrier (electron) current density and minority carrier (hole) current density, we concluded that the oxidation of the electrodes contributes positively to the cell performance since the electrode-electrolyte interface shows unipolar Schottky diode characteristics. Copyright (C) 2001 John Wiley & Sons, Ltd.