Science Opens Routes to Energy Recycling

Molecular biology has been used by scientists in the US to make a catalyst that can split water into hydrogen and oxygen.  It means that a truly renewable biotechnological material could be used to help cars run on water.

In China chemists have announced a nanofabric – a catalyst put together atoms at a time – that could begin the process of turning the greenhouse gas carbon dioxide back into fuel.

And with what seems like perfect timing, a new technological venture in Switzerland hopes to be the first commercial plant to harvest carbon dioxide from the air.

The first two propositions are still in the laboratory stage, and [a] third has yet to prove its viability. But the laboratory advances keep alive the hopes of the ultimate in energy recycling.

In the first process, water provides the energy for a chemical reaction that propels a vehicle, and then ends up again as water from the exhaust pipe of a car.  And in the second, a gas released as emissions from fossil fuel could get turned back into fuel.

Platinum catalyst
The hydrogen fuel cell long ago began to deliver energy for manned space flight, and is already in use in urban public transport, with a platinum catalyst fusing hydrogen fuel and oxygen from the air to release electrical energy and water.

But platinum is rare and costly to mine.  And hydrogen, although the commonest element in the universe, is tricky stuff to handle in bulk.

Trevor Douglas, professor of chemistry at the University of Indiana, US, and colleagues report in Nature Chemistry that they exploited the capacity of a virus to self-assemble genetic building blocks and incorporate a very sensitive enzyme called hydrogenase that can absorb protons and spit out hydrogen gas.  They have dubbed it P22-Hyd.

“The end result is a virus-like particle that behaves the same as a highly sophisticated material that catalyses the production of hydrogen,” Professor Douglas explains.

“The material is comparable to platinum, except that it’s truly renewable.  You don’t need to mine it; you can create it at room temperature on a massive scale using fermentation technology.  It’s biodegradable.  It’s a very green process to make a high-end sustainable material.”

P22-Hyd works in two directions:  it breaks the chemical bonds of water to make hydrogen, and it works in reverse to recombine hydrogen and oxygen to generate power.  So it could be used both to make hydrogen and to burn it.
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Attempts to capture carbon have not been promising so far, and the technology required to turn carbon dioxide back into something that burns is still in its infancy.

Atomic structure
But Shan Gao and research colleagues at the Hefei National Laboratory for Physics at the Microscale, China, report in Nature journal that they have found a way to arrange the atomic structure of cobalt and cobalt oxide to turn the metal into something that can more efficiently “reduce” carbon dioxide into the raw material for high-value chemicals − one of which would be liquid fuel.

Importantly, the new arrangement of cobalt and cobalt oxide is in layers only four atoms thick, and it is this exquisitely refined structure that enables the process of reduction to begin at low energies – which in turn could make it a practical tool for conversion of large quantities of captured carbon dioxide into something of value.

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