Indium Tin-Doped Oxide (ITO) as a High Activity Water Oxidation Photoanode

Photochemical water oxidation was carried out at a mesoporous nanoparticle film composed of indium tin-doped oxide (nanoITO). Annealing nanoITO at temperatures above 250 °C affects both conducting and semiconducting properties. Impressive photoelectrochemical activity was observed at this degenerate n-type semiconductor electrode, outperforming the traditional semiconductor titanium dioxide (TiO₂) under the same conditions. In a 0.1 M HNO₃ solution, the nanoITO electrode sustained photocurrents of 1.0 mA/cm² at an E_applied = 1.5 V vs saturated calomel electrode (SCE) (η = 0.55 V) under a 90 mW/cm² UV illumination (375 nm). This activity is compared to ∼0.3 mA/cm² with a traditional TiO₂ electrode under the same potential and conditions. Evidence for oxygen generation in the photolysis experiments was quantified using the collector-generator method, and >70% photocurrent efficiency for O₂ production was confirmed at this nanoITO photoanode.