Solar paint breakthrough produces hydrogen energy

Researchers at RMIT have developed a solar paint that can absorb water vapour and split it to generate hydrogen – the cleanest source of energy.

The paint contains a newly developed compound that acts like silica gel, which is used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry.

But unlike silica gel, the new material, synthetic molybdenum-sulphide, also acts as a semi-conductor and catalyses the splitting of water atoms into hydrogen and oxygen.

RMIT lead researcher Dr Torben Daeneke said: “We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air.

“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.

“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 says the system has been formatted as an ink or paint “that can literally be painted on any surface”.

“You can imagine a brick wall that is transformed into hydrogen-producing real estate.”

What is yet to happen is the development of a method of capturing the hydrogen.

One idea is to use a hydrogen-permeable silicon rubber membrane.

“We’re already making them in our lab for other purposes.”

The system has only been tested in a lab environment, so final figures could be far off what would be produced in a final system, but so far about 5-10 litres of hydrogen gas can be produced per day over an average day, which Daeneke says is not insignificant.

The best areas for production are those that aren’t hit by direct sunlight, which Daeneke says makes it perfect to use “where it is not economical to use solar PV”.

“They work together. It’s an additional ingredient to what is already out there.”

His colleague, Distinguished Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of energy and could be used in fuel cells as well as conventional combustion engines as an alternative to fossil fuels.

“This system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapour can then be absorbed to produce fuel.

“This is an extraordinary concept – making fuel from the sun and water vapour in the air.”

The research has been published as “Surface Water Dependent Properties of Sulfur Rich Molybdenum Sulphides – Electrolyteless Gas Phase Water Splitting” in ACS Nano, a journal of the American Chemical Society.

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