Photoelectrochemical Properties of Titanium Dioxide Electrodes Prepared from a Titanium-Aluminum Alloy

Titanium dioxide electrodes, prepared from titanium-aluminum alloy on a titanium sheet, were examined for photosensitized processes using adsorbed dye molecules, and for photoanodic oxidation of water by direct bandgap excitation. For the photosensitized reactions, which employed ruthenium(II) tris(2-2′-bipyridine-4-4′-dicarboxylic acid) or the iron complex, Prussian blue, the alloy-derived electrode showed photocurrents one to two orders of magnitude higher than for an electrode prepared by oxidation of an unalloyed titanium sheet. Scanning electron micrographs suggest that the high efficiency of the alloy-derived electrode is due to the rough and cracked TiO₂ surface. However, for the water oxidation reaction, the differences were much smaller. The different behavior between the photosensitized reactions under sub-bandgap excitation and water photo-oxidation by direct bandgap excitation could be explained by the greater effectiveness of the rough electrode surface in utilization of the adsorbed dye molecules. For the alloy-derived electrodes, photosensitized currents were optimized by varying the temperature used to form the alloy and to oxidize the titanium sheet, and varying the extent of doping.