Stabilization of p-GaAs electrode surfaces in organic solvent by bi-phenyl rings for spin dependent electron transfer studies

M Tamski,J.-P Ansermet,C Roussel

doi:10.1016/j.jphotochem.2020.112853

Abstract

Biphenyl-4-thiol (B4t) functionalised p-GaAs photocathodes were compared to non-functionalised p-GaAs ones in the presence of methyl viologen cation radical (MV+) as a redox mediator. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies revealed that at bare p-GaAs photocathodes the radical interacts strongly with the electrode surface, displaying unwanted surface states (SS) mediated electron transfer (ET) even in the dark. Functionalising the electrode with B4t passivated the interface against this unwanted process, while ensuring that the conduction band (CB) electrons still facilitated faradaic reduction of MV+ to MV0 with unhindered efficiency.

Highlights

The dark process that was observed for the non-functionalised p-doped GaAs (p-GaAs) has vanished completely, suggesting that the SS mediated hole transfer has been suppressed and that the surface is stable towards MV+
This issue is especially prevalent in the case of p-GaAs, where the majority charge carriers are holes. p-doped GaAs (p-GaAs) is reported as an interesting material for spin l dependent electrochemical studies,[14,15] our field of interest. a In our approach, a spin-oriented electron transfer (ET) is induced from a p-GaAs semiconductor to a radical redox mediator polarized in solution by a magnetic field
We recently reported on the spin dependent ET at chiral and non-chiral electrodes using methyl viologen cation radical (MV+) as redox mediator to explore chirality-induced spin selectivity (CISS).[16]

Summary

Introduction

The dark process that was observed for the non-functionalised p-GaAs has vanished completely, suggesting that the SS mediated hole transfer has been suppressed and that the surface is stable towards MV+.

Results

Conclusion