A new device creates hydrogen from air
Researchers have developed a way to generate hydrogen from air, decoupling production from freshwater resources and providing a new direction for a carbon-free future.
Hydrogen – green hydrogen in particular – is generally agreed to be the ultimate clean energy.
Unlike fossil fuels, which we know contribute to the large-scale CO2 emissions causing global warming, burning hydrogen doesn’t release carbon dioxide or any other greenhouse gases.
Green hydrogen goes a step further by using renewable energies in production.
Like conventional hydrogen production, it is collected through a process called electrolysis, in which water is split into hydrogen and oxygen using a power source. But here, that power is from renewable sources – whether solar, wind, geothermal or tidal.
Since hydrogen can ‘store’ power produced by renewable sources, it complements renewables by offering a continuous supply of power.
So promising is green hydrogen for a low-carbon economy, many see it as Australia’s next great export, due to its ample source of solar and wind.
FRESH WATER OR HYDROGEN?
But producing hydrogen through water electrolysis relies on a very clean water supply, which is a scarce commodity. According to UN-Water, 2.3 billion people live in water-stressed countries, of which 733 million live in high and critically water-stressed countries (UN-Water, 2021).
Already, industrial power plants, agriculture and other industries use a substantial amount of water, which is competing with supply for the human population. Purification processes are possible, but they add complexity and cost to hydrogen production that challenges feasibility.
Then there is the geographic mismatch between renewable electricity and freshwater availability. Areas rich in solar and wind and therefore ideal for green hydrogen production, often suffer water shortage, making competition for fresh drinking water even higher stakes. Places like this include much of middle Asia, West Asia, and India, North Africa, West of North America, and a large part of Australia.
Bringing water in as an alternative not only poses logistical challenges, but may not be possible as shortage increases. An entire hydrogen-based economy would certainly increase the global risk of freshwater shortage.
TURNING AIR INTO HYDROGEN
Researchers at the University of Melbourne are close to providing a way to overcome these issues, with a working prototype of a device that produces hydrogen without consuming freshwater resources.
The technology, which was recently published in Nature Communications, is called Direct Air Electrolyser (DAE) and works by draining water directly from the air before then going through the standard electrolysis process.
Lead researcher Dr Kevin Gang Li, a senior lecturer in Chemical Engineering, says the idea came to him while considering hydrogen production where water supply presents a challenge.
“We see an area that has no groundwater and think it’s unsuitable for hydrogen production. But there is always abundant fresh water in air.”
“Even Alice Springs, which is in part of desert, has around 20 per cent relative humidity. This is more than enough for us to produce hydrogen onsite using renewable energy.”
The DAE, which Dr Li has been working on with PhD student, Jining Guo, is like other electrolysers in that it is made of a panel of metal plates – the electrodes – which supply a current (taken from renewables) for the water splitting process.
But the secret is the porous medium between the plates which is soaked with hygroscopic ionic solution – a chemical that can absorb moisture from air spontaneously.
“It’s simple, but this material likes to take water molecules from the air. When they’ve been taken from air, they become liquid and ready for electrolysis. That’s the core of this invention.”
“If you expose the device to air, it will produce hydrogen. That’s why we call it Direct Air Electrolyser. You use air as the feed to the device, not liquid water like electrolysers currently do.”
It appears to be the first report of pure hydrogen production directly from the air. Read more
