Solar paint turns wall into a fuel station

Article by Adam Duckett

ONE day, fuel stations could become little more than a wall coated with a special catalytic paint, thanks to a novel hydrogen-production system developed by researchers at Australia’s RMIT University.

The paint absorbs water and uses sunlight to split it to produce hydrogen, which could be collected and used as fuel in vehicles, or as a feedstock for industry.

This so-called “solar paint” is made possible by combining two components. The first is a new catalytic material developed by the team – synthetic molybdenum sulphide – which acts like the silica gel used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry. The second is titanium dioxide, which absorbs high-energy UV light and transfers its energy to the catalyst where it is used to split the water it has absorbed.

“Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy-harvesting and fuel-production real estate,” says lead researcher Torben Daeneke.

“Our new development has a big range of advantages,” he said. “There’s no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel.”

Daeneke told The Chemical Engineer that from tests he estimates that several litres of hydrogen would be produced in a typical day on a surface of a few square meters.

“While this does not sound like a lot, there is a lot of energy in a litre of hydrogen. Will this be enough to drive a car over long distances? Maybe not at this stage, but we are keen to increase the efficiency of the system.”

A key barrier to the system being used in the real world will be developing an economical method of collecting the hydrogen that is produced. The team applied the paint on the inside of a clear reactor during laboratory tests, but Daeneke said the costs of using glass at scale would likely be too high.

“To use the solar paint in a practical application we would have to incorporate additional layers to the system. These layers would need to include membranes that allow capturing the produced hydrogen. The good news is that such membranes already exist and would only need to be optimised for this specific application. Many of these existing membranes are transparent and could be applied as a simple additional coating on top of the paint. Alternatively a laminate might be designed containing the active solar paint together with additional layers that take care of the gas handling,” Daeneke said.

The team will now turn its attention to developing its collection method and increasing the system’s efficiency.

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Article by Adam Duckett

Editor, The Chemical Engineer

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