Electron Transfer Reactions at n‐GaP (100) and (111) in Acetonitrile Solutions Facilitated by Cation Adsorption

Electron transfer reactions occurring at n‐GaP (111) and (100) electrodes have been investigated in acetonitrile solutions. In the presence of strongly oxidising cations, such as 10‐methylphenothiazine (10‐MP +· ), Ferrocene (Cp 2 Fe + ) and tetrathiafulvalen (TTF +· ), it is shown that electron transfer proceeds directly from the conduction band to cations adsorbed at the semiconductor surface. Differential capacitance and photo/dark‐current measurements have been used to identify a considerable positive shift of the flatband potential ( U FB ) in the presence of the oxidising cation. This phenomenon is absent in the presence of a similarly oxidising neutral species. No evidence was obtained to support the model which proposes mediated electron transfer via surface states deep in the band gap.