UK scientists have made hydrogen from water in a simple experiment on a lab bench.

Fraser Armstrong, at the University of Oxford, and colleagues attached an enzyme and a light-harvesting dye to titanium dioxide particles to make a hydrogen-producing system powered by sunlight.

When light shines on the system, the titanium dioxide-bound enzyme produces hydrogen from water

Hydrogen is a promising future fuel because its production uses two globally abundant resources - water and sunlight, explains Erwin Reisner, from the Armstrong group. Generating hydrogen requires efficient catalysts, which need to be attached to light-trapping particles. 'There is a search for catalysts that do not use rare, expensive metals such as platinum,' says Reisner. 'Enzymes have long been a source of inspiration.'

Researchers have found that platinum catalysts can be replaced with hydrogenase enzymes that have nickel and iron in their active sites. But these hydrogenases are inhibited by oxygen and also the hydrogen they produce. Instead, Armstrong's team used a selenium-containing hydrogenase that is more tolerant to oxygen and hydrogen and binds strongly to titanium dioxide. They put the catalytic system in a water and buffer solution, which provided electrons and protons. When they shone light on the system, it produced hydrogen.

Michael Hambourger, who designs bio-inspired devices for solar energy conversion and catalysis in Thomas Moore's lab at Arizona State University, Tempe, US, says the construct is ingenious. 'The stability of this hydrogenase when adsorbed on the titanium dioxide surface is intriguing,' he comments.

Reisner says that although the principle has been proved to work, scaling it up to make it a commercial reality will be a challenge. He wants to incorporate a water oxidation catalyst into the device, which he hopes will allow water splitting, producing both hydrogen and oxygen.

Fay Riordan

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