La(M,Ti)(O,N) 3 (M = Zn, Ga) as visible light-driven photocatalyst for water splitting

The use of solar energy is of highest interest from a low environmental impact viewpoint, and nowadays the photocatalytic splitting of water under solar radiations is a challenging and promising domain of research to provide clean and renewable H 2 as an alternative energy resource [1]. Current oxide photocatalysts (TiO 2 , ZnO, SrTiO 3 , NaTaO 3 ...) are wide-gap semiconductors for which UV-light is necessary to produce electron-hole pairs by photoexcitation. Therefore, the development of visible-light-driven photocatalysts for overall water splitting is currently attracting much attention as a potential efficient utilization of solar energy. So far the (oxy)nitride approach become attractive and promising for this specific issue as a consequence of the anionic N 3- /O 2- substitution results in an increase of the covalent character which is illustrated by a shift of the absorption edge towards higher wavelength values (band gap < 3 eV). However other requirements have to be considered to synthesize an efficient visible-light-driven photocatalyst such as the mobility of the photogenerated charge carriers, the crystal structure or the chemical stability. Perovskite-type oxynitrides containing lanthanides and d 0 metal ions such as LaTiO 2 N exhibit interesting photocatalytic behavior as well as d 10 -type metal oxynitrides and sulfides, for instance (Zn,Ga)(O,N) and ZnS systems. Here, we have studied the monoclinic perovskite-type oxynitride system La 2 M 1-x Ti 1+x (O,N) 6 (M = Zn, Ga). It is expected that the expanded nature of the ns band of the d 10 metals improves the mobility of the photogenerated carriers thus enhancing the photocatalytic activity of the material [2]. The effect of the M/Ti substitution on the photocatalytic decomposition of water is investigated. References : [1] K. Maeda, J. Photochem. Photobiol. C: Photochem. Reviews 58-59 (2011) p. 443-446 [2] J. Yin, Z. Zou, J. Ye, J. Phys. Chem. B 108 (2004) p. 12790-12794