TAFEL PLOTS FROM ILLUMINATED PHOTOELECTRODES - A NEW INSIGHT INTO CHARGE-TRANSFER MECHANISM

The mechanism of charge transfer resulting in hydrogen evolution is investigated on bare and metal-(Pt, Au, Ag, Cu, Pb) coated p- and n-type indium phosphide. The metals were deposited by (photo)electrochemical means. Flatband potentials of p-InP are determined in the dark and under illumination. The flatband potential shift of illuminated electrodes is a logarithmic function of the photocurrent density and can be presented in Tafel plots. Slopes as well as intercepts of such Tafel plots reflect the electrocatalytic properties of the catalyst deposit. An analytical expression for the current-voltage curves and the flatband potential shift is derived which accounts for Schottky diode properties as well as for interfacial charge transfer. © 1990, The Electrochemical Society, Inc. All rights reserved.