Visible-light hydrogen generation using as photocatalysts layered titanates incorporating in the intergallery space ruthenium tris(bipyridyl) and methyl viologen.

A series of layered titanates containing in the interlayer space tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] or methyl viologen (MV(2+)) or both has been prepared and characterized by elemental analyses, XRD, and optical and vibrational spectroscopy. Incorporation of Ru(bpy)(3)(2+) and MV(2+) is confirmed by the increase of the distance between the titanate layers. The presence of Ru(bpy)(3)(2+) in the material is also revealed in optical spectroscopy where the ligand to metal charge transfer band appearing at λ(max) 460 nm is observed. Also incorporation of MV(2+) leads to the observation of the charge transfer complex band with the titanate host from 350 to 650 nm. These solids are active for the photocatalytic hydrogen generation from water when colloidal platinum as catalyst and EDTA as sacrificial electron donor are present in the solution. The maximum efficiency was obtained for a solid consisting of layered titanate containing a 10.2 wt.% loading of Ru(bpy)(3)(2+) incorporated in the titanate layers and MV(2+) and Pt nanoparticles in the aqueous solution. This heterogeneous system produced about one-half the hydrogen generated for the conventional homogeneous system where all the components [Ru(bpy)(3)(2+), MV(2+), Pt, and EDTA] are in solution, with the advantage that it can be used as film or recovered by filtration from the aqueous medium.