Application of a diamond thin film as a transparent electrode for in situ infrared spectroelectrochemistry

This paper describes the application of a conducting diamond film as a tran sparent electrode for attenuated total reflectance infrared (ATR-IR) spectr oscopy during electrochemical experiments. The electrode consists of a cond ucting polycrystalline thin film of diamond (4-6 mum) deposited on a silico n wafer (similar to 50 mum). The electrode is pressed onto a ZnSe ATR cryst al with the silicon side in contact with the crystal; electrolyte (0.5 M H2 SO4) is in contact with the diamond film. We then electrochemically polariz e the electrode and observe IR changes at the diamond-electrolyte interface . Before polarization, the IR spectra clearly show the presence of water an d H2SO4 bands of the electrolyte. After conditioning the diamond film with cyclic voltammetry, two IR features appear in the spectra, and we have assi gned to them the formation of -OH groups on the surface. One feature appear s at 3240 cm(-1) (O-H stretch) and the other appears at 1100 cm(-1) (C-O st retch). These features clearly change with polarization potential, but may also depend on the amount of time spent at a critical potential. Because of their wide potential window for electrochemical reactions and their wide s pectral transparency, diamond electrodes should be useful in many other spe ctroelectrochemical studies. (C) 2001 The Electrochemical Society.