Breakthrough in using sunlight to split water

16:40 April 16, 2010

MIT researchers have created a virus-templated catalyst solution used to harness energy from water (Photo: Dominick Reuter )

A team of MIT researchers has managed to mimic the photosynthetic process in plants by engineering M13, a simple and harmless virus, to help splitting water into its two atomic components - hydrogen and oxygen - using sunlight. The researchers hope this is the first step toward using sunlight to create hydrogen reserves that could then be used to generate electricity or even produce liquid fuels for transportation.

Other researchers had already produced systems that use electricity to split water molecules but, as the team explained in a Paper published in the journal Nature Nanotechnology, the difference is that here the system is based on biology, using sunlight to power the reaction directly rather than by using electricity.

The approach that proved the best was to mimic the processes that take place in plants, rather than simply borrowing their components and re-adapt them like others had done before. In plants, chlorophyll absorbs sunlight while catalysts promote the water-splitting reaction. The team decided to engineer a bacterial virus called M13 so that it became wire-like and could very efficiently split the oxygen from water molecules.

The virus acts as the chlorophyl by capturing light, then transfers the energy down its length, acting like a wire. The wire-like structure of the viruses also allows the light-absorbing pigments and catalysts to line up with the right spacing to trigger the water-splitting reaction, drastically improving the system's efficiency.

But according to Professor of Materials Chemistry and Physics Thomas Mallouk, who was not part of the research team, there are still problems to be tackle before artificial photosynthetic systems such as this could be useful for practical energy conversion. To be cost-competitive with other approaches to solar power, the system would need to be at least 10 times more efficient than natural photosynthesis, be able to repeat the reaction almost indefinitely, and be built from cheaper materials. While achieving these objectives will take time, this first apparatus from MIT is undoubtedly still a big step toward solving the problem.

In the current system, the hydrogen atoms from the water get split into their component protons and electrons, but a second part of the system, which the team hopes to develop within the next two years, would combine these back into hydrogen atoms and molecules so that hydrogen could be both produced and stored.