Dye-sensitized semiconductor photoelectrochemical cells for overall water splitting

Photocatalytic water splitting has been one of the grand challenges of chemical research. Since the first discovery of photoassisted water electrolysis using ultraviolet light in 1972, there have been many reports on oxide photocatalysts. However, there has been little progress on molecule-oxide water splitting systems. These photosensitizers can act as visible light absorber and linker to couple photocatalytic nanoparticles and the semiconductor films to build an organic-inorganic hybrid photocatalytic water splitting system. We recently reported that IrO₂nH₂O (1-3 nm diameter) nanoparticles can be stabilized by Ru-tris(bipyridyl) complexes and studied their performance as oxygen evolving photocatalysts . These results inspired us to construct an overall water splitting dye-sensitized cell. The quantum efficiency of the system is quite low (0.8%) due to rapid back electron transfer from TiO₂ to the oxidized sensitizer. We are currently exploring different buffers and investigating composite metal oxide films for a more efficient water splitting system.