Electrochimica Acta 50 (2005) 4605–4608 Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD I. Justicia a , G. Garcia a,∗ , G.A. Battiston b , R. Gerbasi b , F. Ager c , M. Guerra d , J. Caixach d , J.A. Pardo a , J. Rivera d , A. Figueras a,e a ICMAB/CSIC, Campus UAB, 08193 Bellaterra, Spain b ICIS/CNR, Corso Stati Uniti 4, 35127 Padova, Italy c CNA/CSIC Parque Tecnol´ ogico Cartuja 93, Avda Thomas A, Edison, 41092 Sevilla, Spain d IIQAB/CSIC Jordi Girona, 18 08034 Barcelona, Spain e Instituto de F´ ısica, UNAM, Campus UNAM Juriquilla, 76230 Quer´ etaro, Mexico Received 15 January 2004; received in revised form 14 September 2004; accepted 15 October 2004 Available online 11 July 2005 Abstract Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO 2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters. © 2005 Elsevier Ltd. All rights reserved. Keywords: Photocatalysis; Visible light; MOCVD; Thin films; TiO 2 1. Introduction The great environmental need to eliminate pollutants makes the search for new catalyst materials, with improved properties and efficiencies, a very important topic. Semicon- ducting TiO 2 has proved to be an excellent photocatalyst, which allows the degradation and ultimately the mineralisa- tion of stable organic pollutants, such as detergents, dyes and pesticides in water [1,2]. However, the large energy needed to activate the photocatalysis for the anatase phase (3.2 eV) requires the use of UV light instead of the cheaper and more readily available energy source, such as the solar spectrum or even interior lighting. ∗ Corresponding author. Tel.: +34 935801853; fax: +34 935805729. E-mail address: gemma@icmab.es (G. Garcia). The manufacturing of such a catalyst material relates to another aspect of the problem. Usually, aqueous suspensions and powders are used, making the recovery of the active material complicated and expensive. The possible industrial applications of any photocatalyst require thus a new material, with lower band gap energy, that can be easily recovered. The objectives of our work consist in demonstrating that titania band gap energy can be lowered by inducing oxygen sub- stoichiometry in the lattice along with the fact that the best way to prepare such a material will be as a thin film. In a previous paper [3], by using theoretical calculations, we had pointed out the possibility of introducing within the TiO 2 band gap, states that absorb visible light by autodop- ing the anatase material. The insertion of oxygen vacancies in the anatase structure induces the defect band to reach a width of 0.2eV, starting to overlap with the conduction 0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2004.10.096