Device 100 times thinner than a human hair helps scientists turn water into fuel

A device one hundred times thinner than a human hair has helped scientists transform water into fuel.

The revolutionary technique mimics the human lung – and could rival wind and solar power for creating clean energy.

Inspired by the way our bodies breath in and out, it splits water to produce fuel cells – the only by products of which are electricity and heat.

The first process – similar to exhalation – produces hydrogen, a clean gas, by oxidising water molecules in the anode of a battery.

The second is more like inhalation and generates energy through a reaction that consumes oxygen.

Fuel cells are composed of an anode, a cathode and an electrolyte membrane. Hydrogen and oxygen pass through the anode and cathode, respectively.

The act of breathing is so automatic for most organisms it could be mistaken as simple, said the researchers.

But it is actually one of the most sophisticated systems for the exchange of gases found in nature.

With each breath air moves through the lungs until it reaches minute sacs called alveoli.

From there, the gas must pass into the bloodstream without diffusing – which would cause harmful bubbles to form.

It is the unique structure of the alveoli that stops this and makes the gas interaction highly efficient.

This includes a membrane – a hundred times thinner than a human hair – that repels water molecules on the inside while attracting them on the outer surface.

Lab members at the Department of Materials Science and Engineering at Stanford University, California, drew inspiration from this to create better ‘electrocatalysts.’

These are materials that increase the rate of a chemical reaction, known as catalysis, at an electrode or conductor, explained first author Professor Jun Li.

He said: “Clean energy technologies have demonstrated the capability of fast gas reactant delivery to the reaction interface.

“But the reverse pathway – efficient gas product evolution from the catalyst-electrolyte interface – remains challenging.”

Oxygen and hydrogen gases are rapidly produced and transported through the thin, alveolus-like membrane – which is one hundred times thinner than a human hair.

Made from the common household plastic polythene, it also prevents the formation of any energy sapping bubbles.

The oxygen is delivered to the catalyst at the surface of the electrode during chemical reactions.

Prof Li, whose findings are published in the journal Joule, said the electrocatalytic mechanism “works like a mammalian lung” to convert water into fuel.

He added: “It could help existing clean energy technologies run more efficiently.

“It structurally mimics the alveolus and carries out two different processes to improve the reactions that drive sustainable technologies such as fuel cells.

“Although it is still in the early phases of development, the design appears to be promising.

“The uncommonly thin nano-polyethylene membrane remains hydrophobic longer than conventional carbon-based gas diffusion layers, and this model is able to achieve higher current density rates than conventional designs.”

But the lung-inspired design still has some room for improvement before it will be ready for commercial use.

Since the ultra thin membrane is made of plastic it cannot tolerate temperatures higher than 100 degrees Celsius.

“This could limit its applications,” said Prof Li.

His team believe this material may be replaced with similarly thin non porous hydrophobic membranes capable of withstanding greater heat.

They are also interested in incorporating other electrocatalysts into the device design to fully explore their capabilities.

Prof Li added: “The breathing-mimicking structure could be coupled with many other state-of-the-art electrocatalysts, and further exploration of the gas-liquid-solid three-phase electrode offers exciting opportunities for catalysis.”

By Mark Waghorn

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