A study of S-doped TiO 2 for photoelectrochemical hydrogen generation from water L. K. Randeniya Æ A. B. Murphy Æ I. C. Plumb Received: 5 April 2007 / Accepted: 12 November 2007 / Published online: 12 December 2007 Ó Springer Science+Business Media, LLC 2007 Abstract Sulfur-doped titanium dioxide (TiO 2 ) was investigated as a potential catalyst for photoelectrochemical hydrogen generation. Three preparation techniques were used: first ballmilling sulfur powder with Degussa P25 powder (P25), second, ball milling thiourea with P25, and third a sol–gel technique involving titanium (IV) butoxide and thiourea. The resulting powders were heat-treated and thin-film electrodes were prepared. In all three cases, the heat-treated powders contained small amounts of S (1–3%). However, Rietveld analysis on X-ray diffraction (XRD) measurements revealed no significant changes in lattice parameters. For the samples prepared using thiourea, X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of N and C in the heat-treated powders in addition to S. In all cases, visible-ultraviolet spectroscopy performed on bulk powders confirmed the extension of absorption into the visible region. However, the same spectroscopic technique performed on thin-film electrodes (*0.5 lm) suggests that the absorption coefficients were very small in the visible region (B10 4 m -1 ). The first and third methods yielded powders with substantially smaller photocatalytic activity relative to P25 powder in the UV region. The electrodes prepared from powders obtained using the second method yielded photocurrents comparable to those prepared from P25 powder. Introduction For photoelectrochemical hydrogen production, a photo- electrode material is required with an appropriate band gap to harvest as much of the incoming solar radiation as possible. The material needs to have good optical absorp- tion, be stable in strong electrolytes, have efficient electronic charge transfer and suitable energetics (location of conduction and valence band edges), and be inexpensive and readily available. Titanium dioxide (TiO 2 ) satisfies most of the above requirements. Its main shortcoming is that its relatively large band gap (3.0 eV for the rutile form) means that the fraction of the incoming photons from the sun at the surface of the earth that are able to excite electrons across the band gap is only 2.3%. If the band gap of TiO 2 could be lowered to close to the ideal value for water splitting (approximately 2 eV), without seriously impacting on its favorable energetics, photo-stability, or charge transfer efficiency, it should be possible to approach the US Department of Energy goal of 10% efficiency for photoelectrochemical hydrogen production from sunlight. There have been many studies investigating the reduc- tion of the band gap of TiO 2 by doping with anions. Asahi et al. [1] calculated densities of states for anatase TiO 2 with substitutional doping of C, N, F, P, or S for O. They found that S-doping produced similar bandgap narrowing to that of N-doping, but suggested that it would be difficult to incorporate S into TiO 2 . However, there are several studies in the recent literature which claim that the incor- poration of S atoms into the TiO 2 lattice has been achieved [12, 18–21, 32, 35, 36]. It should be noted however that out of all these studies, only one, that of Chandra Babu and Srivastava, [3] investigated the use of S-doped materials for photoelectrochemical hydrogen production. In the present study, we report the use of three different techniques to obtain S-doped TiO 2 powders and investigate their suitability for efficient water splitting, under both UV and visible illumination. The powders, and electrodes formed from the powders, are characterized by XRD, XPS, L. K. Randeniya (&)  A. B. Murphy  I. C. Plumb CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070, Australia e-mail: Lakshman.Randeniya@csiro.au 123 J Mater Sci (2008) 43:1389–1399 DOI 10.1007/s10853-007-2309-z