TiO2-Mediated Photoelectrocatalytic Purification of Water

Sol-gel processing methods were employed to coat thin, porous films of titania on metal plates, specifically on aluminum, 304 stainless steel, and titanium. After coating and firing, all of these materials displayed photocatalytic activity when tested with a solution of formic acid that contained dissolved sodium chloride. However, only the titanium-supported photoelectrodes were stable with repeated use. Activities of these titaniumsupported photoelectrodes increased, often by factors of two to three, when positive potentials were applied across the titania coatings. Electrode activities increased when multiple coatings of titania were applied to the electrodes, although electrode stability was problematic when multiple coatings were deposited. Photoelectrocatalytic activities were not inhibited significantly by the presence of sodium chloride in the test solutions, while copper could be deposited on platinum cathodes when the test solutions contained dissolved copper in addition to sodium chloride and formic acid.