Over the past decade a number of significant advances have been made in the development of viable artificial photosystems for water splitting. Antenna complexes offer systems that can collect solar energy over large spatial regions and funnel it to specific sites for charge-separation. New methods exist for extending the excited state lifetimes for Rubpy based sensitizers and numerous studies have shown that the charge separation event can be directed towards specific donor and acceptor 'cofactors'. Advances in our ability to collect and store multiple electrons or holes, suggests that the catalytically desirable multi-electron reactions for HER and OER can be accessed. Molecular dyads and triads containing potentially catalytic active reaction centers have been constructed and shown to be active towards photochemi-
cally induced electron transfer reactions. This and the development of new and better catalysts for both OER and HER suggests that photocatalytic assemblies are not long in coming.
The current state of the art is evolving however some notable problems remain. Current catalysts are slow and inefficient compared to their biological counterparts. Challenges remain in coupling the multi-electron equivalency in the OER and HER with the Rubpy sensitizers. Back electron transfer or related wasteful back reactions still account for the serious losses in efficiency. These issues will be difficult if not impossible to address in a single compartment molecular system. Compartmentaliza-tion coupled to vectoral electron transfer remains a largely unexplored aspect of this work (if heterogeneous systems are excluded) yet is likely to be critical for success for a purely molecular system.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.