Investigation of CdS Photoanode Reaction in the Electrolyte Solution Containing Sulfide Ion

Abstract

Abstract The study of the photoanodic reaction in the CdS/S2− system was carried out by means of the rotating ring-disk electrode (RRDE) technique. The photoanodic reactions at an n-type CdS electrode are divided into two types; the photoanodic oxidation of redox agents in the electrolyte solution and the photoanodic dissolution of CdS electrode surface. The stabilization of a CdS photoanode could be attained through the preferential progress of the former of these two processes. The ratio between these two processes depends upon the concentration of S2− in the electrolyte solution and the light intensity. Sulfide ion in the electrolyte solution stabilizes CdS photoanode and gives rise to the shift of the flatband potential of CdS electrode by ca. −60 mV/log[S2−]. This dependence of the flatband potential on sulfide ions can be explained by an adsorptive dissociation equilibrium at a CdS electrode surface. The results of the photoanodic reaction were disscussed referring to the charge transfer process with the participation of some surface energy state within a bandgap.