Water splitting into hydrogen and oxygen by sun light is of major importance for the future energy supply. The sustainable production of hydrogen via water splitting requires semiconducting nanoparticles in which electron-hole-pairs are generated upon light absorption. Subsequently, water can be split into the elements at the particle surface, the photon energy is converted into chemical energy. Additionally, the surface of the nanoparticles has to be modified by catalytically active centers to improve the water splitting rate. So far structurally complex catalysts have been empirically developed. We use taylored molecular precursors to generate and functionalize the catalyst in the gas phase. Therefore, specialists for the synthesis of volatile Gallium precursors (Fischer group, Bochum), aerosol based nanoparticle synthesis (Winterer group, Duisburg) and heterogeneous photocatalysis in three phase reactors (Muhler group) cooperate in this project.