Proton reduction to hydrogen in biological and chemical systems

In the drive to devise catalytic systems to convert solar energy into the energy of chemical bonds, chemists and electrochemists are seeking inspiration from our understanding of enzymes involved in bioenergetics. This is particularly true for generating molecular hydrogen from high energy electrons derived from solar driven water splitting. In this case the natural enzymes are the [NiFe]- and [FeFe]-hydrogenases. In this article we review our present understanding of the structure and mechanistic functioning of these enzymes and how they are providing a blue print to the design and understanding of the mechanism of a variety of synthesized catalysts for proton reduction chemistry.