The research project ‘Solar Hydrogen from Air’ won the first Energy Award, presented by Febeliec – the association of industrial energy consumers – to honour an idea that contributes to solving the energy problems of the Belgian industry. The research team consists of Professor Johan Martens (middle), flanked by (from left to right) bioscience engineer Tom Bosserez, Dr Christos Trompoukis, and bioscience engineers Jan Rongé and Lisa Geerts. | © KU Leuven - Rob Stevens

Hydrogen gas has been a green promise for quite some time. It’s a light gas that you can store in a pressurized tank. In a fuel cell, it can be converted straight into electricity. Car manufacturers are already working on an electric car based on hydrogen gas, but a big breakthrough has not yet been made.

That is mainly due to the production of hydrogen gas, says Johan Martens of the KU Leuven Centre for Surface Chemistry and Catalysis. “Hydrogen gas does not occur in nature. It is traditionally derived from fossil fuels, and this process comes with the emission of CO 2 . Research is being conducted into alternative technologies such as electrolysis: you send an electric current through water, and this creates oxygen and hydrogen gas. In itself, this process is not polluting, but it still requires electricity that is often derived from fossil fuels. The current challenge is to find a truly sustainable production method that can compete economically with fossil fuels.”

All-in-one system

The team is the first in the world to produce hydrogen gas using nothing but sunlight and water vapour from the air. “We have already tested our solar cells on the roof, and they work.” In the experimental stage, however, the solar cells make up only a dozen square centimetres.

“The device consists of a reactor with two compartments: light and air enter through one side, and hydrogen gas comes out of the other. Between the two compartments are the paper-thin solar cell, covered with filtering membranes, and catalysts, substances that trigger the production of hydrogen gas. We don’t need to add water, acids, or any other auxiliary substances, and the sunlight provides the energy.”

“In theory, this device could even be used in the desert, because there, too, every cubic metre of air contains about five grammes of water.”

“Our device is unique because it’s an all-in-one system, which uses air as a source of water and directly produces hydrogen gas. The system is also carbon neutral, and there is no net use of water: the device gets the water it needs from the air and releases it back into the air again."

Widely applicable

The production capacity of the new solar cell is currently lower than that of a traditional solar panel, but Johan Martens and his team aim to improve it with further research. Will the device be able to compete with the regular photovoltaic solar panels at some point? “The two systems can coexist. Traditional solar panels generate electricity for immediate use. The strength of our solar cell is in its wide applicability: with hydrogen gas, you can not only generate electricity, you can also use it as a chemical, renewable fuel.”

According to Martens, hydrogen gas even opens up perspectives for the fight against climate change. “We live in a carbon world: there’s no getting around that. We shouldn’t ban carbon emission from our economy. Instead, we can collect the CO 2 that is produced and recycle it to obtain new fuel or usable chemicals.” In this area, hydrogen gas opens up perspectives for the industry, Martens believes. “By adding hydrogen gas to CO 2 you can, for instance, produce synthetic natural gas.”

It’s much more difficult to reduce the carbon footprint of households and vehicles. “But in that area, too, hydrogen gas may play a role. If our solar cell gives each house its own hydrogen gas generator, all energy can be produced locally. Or we could equip the bodywork of cars with our technology to produce hydrogen gas. You could compare it to charging an electric car – except you don’t need a charging point, just sunlight.”

“Chemistry is often frowned upon as a polluting industry, but for a challenge such as climate change, it may very well provide the ultimate solution.”