Daylight robbery

An Oxford University breakthrough could produce unlimited supplies of hydrogen using natural light.

Two teams of researchers at OxfordUniversityhave brought the hydrogen revolution a step closer. One has found a way to generate a potentially unlimited source of hydrogen for fuel cells using only daylight. The other has developed a method of storing hydrogen at a high weight in a hydride that beats previous attempts to release the fuel at low temperatures.

Clean hydrogen generation is a key stumbling block for the realisation of the hydrogen economy and fuel cell use. Reforming fossil fuels can generate hydrogen, but the process produces greenhouse gas carbon as a by-product. Cleaner electrolysis methods can split water into hydrogen and oxygen and be powered by renewable energy, but power sources like solar cells are too expensive and need to improve their efficiency to generate enough electricity to force the reaction.

The OxfordUniversity team placed transition metal nanoparticles inside a microporous oxide material that caused water to split into hydrogen and oxygen in ordinary daylight, without the need for an external electricity source like solar cells to drive the reaction.

Prof Peter Dobson, academic director of BegbrokeSciencePark at Oxford, said the research could lead to a ‘radical breakthrough’ in hydrogen generation that would be simpler and cheaper than coupling a renewable energy source with an electrolysis unit.

‘In principle we could do the entire thing with a simple membrane separator, so in one half of the cell you generate oxygen, the other half hydrogen,’ he said. ‘It would stand unattended, bubbling off hydrogen and oxygen more or less forever until the catalyst is deactivated.’

The next step is to design a device that can separate the hydrogen and oxygen mix produced around the nanoparticles. ‘We’ll have to engineer the gas separation membranes very carefully. We may have to build in a potential gradient to separate the gases,’ said Dobson.

‘If we get the design right we may be able to incorporate catalysts into the membrane so it will run in an unattended fashion.’

Dr Tiancun Xiao, the Oxford inorganic chemist who made the discovery, is setting up a company called Oxford Catalysts to develop the technology.

Elsewhere at Oxford, a team led by Prof Peter Edwards has found a way of storing hydrogen at 8–9 weight per cent in a hydride that releases it again when subjected to temperatures of around 80°C. Hydrides can absorb hydrogen molecules into their structure and release them to power a fuel cell without the need for bulky and inefficient gas or liquid storage.

But previous high weight methods only worked at elevated temperatures of around 200°C or more. The researchers have found a way to create the hydrides via a chemical route, rather than high-velocity ball milling.