MIT Uses Viruses to Turn Water into Hydrogen Fuel

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A computer visualization of
the biologically-based
system shows the virus itself
(in yellow) with molecules of
pigment (in pink) and of the
metal catalyst (brown spheres)
attached to its surface. The
pigment and catalyst cause
water molecules to split apart
when they come in contact.

image via MIT

The team engineered a common, harmless bacterial virus called M13 so that it would attract and bind with molecules of a catalyst (the team used iridium oxide) and a biological pigment (zinc porphyrins). The viruses became wire-like devices that could very efficiently split the oxygen from water molecules.

Over time, however, the virus-wires would clump together and lose their effectiveness, so the researchers added an extra step: encapsulating them in a microgel matrix, so they maintained their uniform arrangement and kept their stability and efficiency.

While hydrogen’s the useful stuff, it’s the splitting of oxygen from water that’s most difficult, so this is where the team focused its efforts.

Other researchers have tried to use the photosynthetic parts of plants directly for harnessing sunlight, but these materials can have structural stability issues.

In the team’s system, the viruses simply act as a kind of scaffolding, causing the pigments and catalysts to line up with the right kind of spacing to trigger the water-splitting reaction.

The role of the pigments is "to act as an antenna to capture the light," explains Angela Belcher, "and then transfer the energy down the length of the virus, like a wire. The virus is a very efficient harvester of light, with these porphyrins attached."

Using the virus to make the system assemble itself improves the efficiency of the oxygen production fourfold. The researchers hope to find a similar biologically based system to perform the other half of the process, the production of hydrogen.

The process still lacks a critical step: once the splitting is complete, the oxygen has been siphoned from the water but the hydrogen is left split into its component electrons and protons.

The team is currently exploring other biomimicking systems that might reassemble those building blocks into usable, storable hydrogen atoms.

Researchers are also working to find a more commonplace, less-expensive material for the catalyst, to replace the relatively rare and costly iridium used in this proof-of-concept study.

An actual commercial process that produces hydrogen from water as efficiently as plants do is likely years away, but the MIT team hopes to have a prototype device that can carry out the whole process of splitting water into oxygen and hydrogen, using a self-sustaining and durable system within two years.

The research is described in a paper published on April 11 in Nature Nanotechnology.

[source: MIT]

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