Artificial Photosynthesis: Molecular Systems for Catalytic Water Oxidation

A chromophore (photosensitizer) can first be attached to a semiconductor in an artificial photosynthetic system. Upon illumination a charge-separated state is formed, by electron transfer from the photoexcited chromophore to the conduction band of the semiconductor. It is important that this charge-separated state is sufficiently long-lived to allow the chromophore to abstract an electron from the catalyst, thus regenerating the chromophore and a one-electron oxidized catalyst. The first step in an artificial photosynthetic system is light-harvesting by a chromophore, that is, a light absorbing component, analogous to the photosynthetic pigments. This chromophore should efficiently absorb and convert the incoming solar energy into an excited state that can transfer an electron to an acceptor for the creation of a charge-separated state, thus generating the required thermodynamic driving force for the desired chemical reactions.