A Novel Composite Anode: The Electrooxidation of Organic Molecules via Formation of Highly Energetic Holes

This paper describes, for the first time, the electrochemical characteristics of a novel, composite electrode, comprising a thin TiO2 layer sandwiched between a silicon wafer and a metal grid. Holes thermally and/or photochemically generated near the Si/TiO2 interface in the Si are able to reach the surface of the TiO2 and oxidize water and/or species in solution. Hole transport across the TiO2 is facilitated by the application of a bias voltage across the silicon and metal grid. At low bias voltages, oxidation of water takes place at the metal grid; at higher voltages, the oxidation takes place directly at the TiO2 as surface states are accessed. The generation of holes is enhanced significantly if the TiO2 surface is irradiated with visible light. A theoretical model is presented to explain the observed data. The anodes represent a completely new area of oxidative electrochemistry with potential application across a wide range of technology, from fuel cells-on-a-chip to electroorganic chemistry.