Hydrogen is one of the current contenders for fuel of the future, to replace the fossil fuels that we have relied on so heavily for some time.   The interconversion of two protons to hydrogen gas is an important reaction for the development of hydrogen as a fuel source, as it is integral to hydrogen based fuel cells and hydrogen production based on photosynthesis or electrolysis.

Nature has developed a series of enzymes, hydrogenases, which catalyse this reaction in living organisms. However, these enzymes are fragile and somewhat air-sensitive.   In their Dalton Transactions Perspective article, Vincent Artero and Marc Fontecave, together with their colleague, Dr Sigolene Canaguier, all based at the Universite Joseph Fourier, Grenoble, France, describe efforts to prepare metal complexes, using the naturally occurring hydrogenases as inspiration.

By producing complexes that mimic the dimetal active site of the hydrogenase, containing both nickel and iron atoms, scientists have in the past tried to produce useful catalysts.   However, Ni-Fe complexes have not yet been prepared that have the required useful catalytic properties.   Artero and Fontecave describe Ni-Ru based complexes, which are easier to prepare, and more stable than their iron counterparts. These complexes do show the desired catalytic activity, although a large overpotential is needed before catalysis can occur.

Future research needs to look again to Nature for inspiration, and consider iron and other first row transition metal complexes.   'Living organisms obviously have selected Fe for its bioavailablity and have found conditions to make it functional,' says Artero.