Charge Transfer Processes at WSe2 Electrodes with pH‐Controlled Stability

Abstract

In aqueous solutions of low pH, the energy bands at the surface of become unpinned upon illumination. The corresponding positive shift of bands is caused by accumulation of holes at the surface. This is understood as being due to a position of the corrosion potential positive of the valence band, which moves in a more negative direction with increasing pH. In acid solutions, the energy bands remain pinned under illumination in the presence of redox systems which have a standard potential located at or negative of the valence bandedge. Experiments with rotating ring disk electrodes have shown that in this case the electrode is completely stable. This is a very promising result with respect to regenerative solar cells, because for the first time a stabilization by a redox couple with a standard redox potential near the valence bandedge of a photocorroding n‐type semiconductor was found. The charge transfer processes at n‐ and p‐type electrodes are analyzed in detail in solutions of different pH.