Photoelectrochemical reactions on semiconductor materials

Abstract

The cathodic reduction of Fe3+ ions and I2 on ann-GaAs electrode was studied. The variation in the current density with the concentration of the oxidant has been interpreted as being the result of a reduction mechanism involving interface or surface states, an interpretation that is amply substantiated by experimental data. The effect of the surface modification with SiW12O404− on the reduction process was studied. Prior to this electrode activation, the rate constant for electrons being transferred from the conduction-band to the interface or surface states,kS, was observed to be independent of electrode potential, whereas in the case of the modifiedn-GaAs,kS depends on band-bending. On the other hand, the rate constant for electrons being transferred from the interface or surface states to oxidant species,kox, does depend on electrode potential in the case of the unmodifiedn-GaAs, and is independent of band-bending in the case of the modifiedn-GaAs. This change may be attributed to the filling of the active surface or interface states or their redistribution after the electrode surface activation.