Photosensitization of semiconductors with transition metal complexes - a route to the photoassisted cleavage of water

Development of artificial (non-biological) devices that achieve fuel generation by visible light is currently an ever growing area of research. Light driven redox reactions on organized assemblies afforded by semiconductor dispersions or colloidal sols provide the impetus. The various strategies used in achieving generation of dihydrogen, H2, from the photodissociation of water are discussed. One important point that is made is dye sensitization of wide bandgap semiconductors to improve their spectral response to visible light. In practical terms, we present three examples from our recent work, in which the semiconductor particle surface (TiO2) has been modified by adsorption of various dye molecules and by surface derivatization with ruthenium(II) complexes. In the latter case, we have demonstrated the feasibility of producing both H2 and O2 in stoichiometric amounts from the cleavage of water, and this without the need for a sacrificial electron donor.