Photoresponse of n-TiO2 thin film and nanowire electrodes

Thin film and nanowire electrodes of n-type titanium oxide (n-TiO2) were fabricated and their photoresponses towards water-splitting reaction were studied. A more than twofold increase in maximum photoconversion efficiency was observed when a single-layer thin film of n-TiO2 was replaced by nanowires. Highest photoconversion efficiency was observed at an applied potential of 0.61 V vs. E-aoc where the electrode potential at open circuit, E-aoc was found to be - 1.0 V SCE-1 at illumination intensity of 40 mW cm(-2) in 5.0M KOH solution. The maximum photoconversion efficiency was approximately of another twofold increase for water splitting at nanowire electrodes when methanol was used as a sacrifacial hole scavenger (depolarizing agent) in the electrolyte. Also, this maximum photoconversion efficiency was found at a lower applied potential of 0.41 V vs. E-aoc in presence of methanol. The band-gap energy of the n-TiO2 films and nanowires annealed at 750degreesC was found to be 2.98 eV, which indicates their rutile structure. (C) 2002 Elsevier Science B.V. All rights reserved.