The Effects of Surface Energetics and Surface Oxide Layers on the Cyclic Voltammetry of Metallocenes at Nonilluminated p ‐ InP Electrodes

Abstract

Electron‐transfer processes at highly doped electrodes were investigated by monitoring the cyclic voltammetric dark currents of a series of metallocenes in acetonitrile solutions. The formal reduction potentials of the metallocenes span the bandgap of , allowing a comparison of the cyclic voltammetric response as a function of the formal reduction potential and the energetic condition of the electrode surface. Since the electron transfer of all of the metallocenes was electrochemically reversible on the timescale of cyclic voltammetry at a platinum electrode, differences in the voltammetric responses at were attributed to processes within the semiconductor or to surface phenomena. The energetic condition of the electrode surface during the cyclic voltammetric experiments was monitored by measurements of the capacitance of the space‐charge region. Although a simple chemical etching and electrochemical cycling procedure yielded reproducible surface energetics, the interface responded ideally to changes in electrode potential over a range of only about 0.8V. Metallocene redox couples with located within that range exhibited reversible cyclic voltammetry when the experiment was performed within that range. The couples with located outside of the ideal range displayed irreversible cyclic voltammetry. Voltammetric responses for electrodes with different crystal orientations and doping densities were compared.