Oxynitrides Perovskites Thin Films : Photoelectrochemical Measurement Under Visible Light
Résumé
The question of finding a clean alternative to conventional energy has become an essential challenge for the scientific community. Hydrogen production by water splitting under visible light is one of the most innovative solutions. H2 production can be achieved, in the UV domain, by broad band-gap semiconducting oxides. The integration of nitrogen in the material's structure has been found to narrow the band gap of the material and thereby extend its photoactivity into the visible range. We have focused our efforts on the preparation and characterization of original LaTiOxNy thin films. The films, deposited by reactive RF magnetron sputtering on Nb-doped SrTiO3 substrates under a range of conditions were found to develop different crystalline structures. Polycrystalline, oriented, or epitaxially grown thin films were thus obtained and tested. The films have been characterized by XRD, EDS, SEM, AFM, and UV-visible spectroscopy. Through current-potential measurements, it was demonstrated that these oxynitride films function as n-type semiconductors with band gaps of 2.05 to 2.35 eV. The modification of the catalyst surface by deposition of a co-catalyst (IrO2) was found to significantly enhance the photocurrent associated with the water oxidation. The band-gap positions of all of the LaTiOxNy films have been determined and are suitable for the oxidation and reduction of water