A sheet-like device extracts water from the air to produce hydrogen fuel

A small circular device modeled after a leaf can extract water from the air to create a clean energy source, a new study shows.

The “transparent porous conductive substrate” (TPCS) is a small circle of compressed glass fibers coated with a thin layer that absorbs light.

When exposed to sunlight, the device extracts water from the air, producing hydrogen gas that could potentially be used as fuel.

The hydrogen gas could be captured and stored in large plants and used when needed, for example to power cars or heat homes, researchers say.

Researchers have developed “novel gas diffusion electrodes” that can convert water vapor in its gaseous state from the air into hydrogen fuel

The research was carried out by chemical engineers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

“To achieve a sustainable society, we need ways to store renewable energy in the form of chemicals that can be used as fuels and raw materials in industry,” said study author Professor Kevin Sivula of EPFL.

“Solar energy is the most abundant form of renewable energy and we strive to develop economically competitive ways to produce solar fuels.

The team was inspired by “how a leaf works”, namely photosynthesis – the process by which plants use sunlight, water and carbon dioxide to create oxygen and energy in the form of sugars.

Scientists have previously performed “artificial photosynthesis” by creating hydrogen fuel from sunlight and liquid water using a device called a photoelectrochemical (PEC) cell.

But Professor Sivula wanted to show that PEC technology can be adapted to harvest water vapor from air rather than liquid water, which could lead to more use cases, for example in humid environments.

To make their TPCS, they started with a type of glass wool, an insulating material made from fiberglass that has a texture similar to textile wool.

The glass wool was processed in a commercial kitchen blender and pressed into circular felt “wafers” by fusing the fibers together at high temperature.

Next, each wafer was coated with a transparent thin film of tin oxide, an inorganic compound known for its excellent conductivity.

They made sure the coating was porous to increase its surface area and maximize contact with water in the air.

Shown is the “transparent porous conductive substrate” (TPS) with and without the light absorbing coating

EPFL’s Professor Kevin Sivula holds the small chamber and one of his ‘transparent porous conductive substrates’.

The wafer was then recoated with a chemical compound called cuprous thiocyanate, a semiconductor material that absorbs sunlight.

This second thin coating still lets light through, although it appears opaque.

‘The semiconductor absorbs the light so it appears dark,’ Professor Sivula told MailOnline.

“Importantly, without the semiconductor coating, we don’t want any light absorption by the electrode, as that would mean it can’t absorb very much light.”

The scientists then built a small chamber with the coated wafer in which to collect the hydrogen.

Researchers say the system works in humid environments where there is a large amount of water vapor in the ambient air.

This could make it ideal for installation in high humidity countries like India, Malaysia, Philippines and Indonesia.

Potentially, large plants containing the system could operate in remote areas of these countries, fueling cars with hydrogen for example.

The scientists also built a small chamber to hold the coated wafer and a membrane to separate the hydrogen gas produced for measurement

Image from the team’s paper. C) and D) show scanning electron micrographs of the morphology of the transparent porous conductive substrate

‘A future implementation of this technology would require hydrogen collection,’ Professor Sivula said.

“However, the chamber could be as simple as a plastic bag or envelope that would contain the gases produced.”

The team’s study, published today in the journal Advanced Materials, marks “only a first phase” in the adoption of this technology.

‘The overall solar to hydrogen efficiency is still quite low, but our invention of the TPCS now opens the door to push this technology further,’ said Professor Sivula.

The researcher said TPCS is currently at a low “technology maturity level,” so it would take 10 years or more to realize a practical device, he estimated.

There is currently no precise information on how much a rollout would cost, although Professor Sivula said the device uses inexpensive materials and processing techniques.

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