Transparent nanoporous tin-oxide film electrode fabricated by anodization

A transparent nanoporous tin oxide film electrode was fabricated by anodizing a tin film on a fluorine-doped tin oxide (FTO) film electrode. The resulting anodized nanoporous tin oxide (ANPTO) film has columnar-type pore channels with around 50 nm in diameter and is optically transparent. Electrochemical measurements with Fe(CN)63− as a redox probe clearly revealed that the ANPTO film could be used for a working electrode with a large internal surface area. Moreover, it was found that ANPTO film had a wider anodic potential window (> ca. 2.0 V) than conventional metal oxide electrodes, such as FTO and indium tin oxide film electrodes (> ca. 1.3 V). The wide anodic potential window improves applicability of a transparent metal oxide electrode for various electrochemical oxidation reactions, which are often interfered by oxygen evolution in water. These results conclude that the ANPTO film can be used as an advanced transparent nanoporous film electrode.