Hydrogen, the most common element in the universe, has long been touted as a clean and plentiful alternative energy source. But the easiest way to produce hydrogen fuel requires pure water, which can be hard to get ahold of — and will only become more difficult to source amid worsening droughts around the globe.
Now, in a study published this week in the journal Nature Communications, scientists have revealed a new way to churn out hydrogen fuel.
What’s new — It turns out that all you need is the humidity that’s naturally hanging in the air, they found, along with their new device that swallows moisture and spits out hydrogen and oxygen. Their method could spur hydrogen fuel production anywhere on the planet.
Here’s the background — When hydrogen reacts with oxygen in electricity-generating fuel cells, it leaves only water behind — unlike fossil fuels, which emit pollutants in the process. Electricity then splits water molecules into hydrogen and oxygen gases, a process that’s known as electrolysis.
Currently, hydrogen research aims to harness solar energy or other renewables to create hydrogen fuel from water, all without harming the environment.
But this strategy "will need a significant amount of freshwater, and this can be a challenge in places where the water supply is a big issue," says study author Gang Kevin Li, a chemical engineer at the University of Melbourne in Australia.
More than a third of Earth's land surface is arid or semi-arid, but these areas nevertheless manage to support roughly 20 percent of the world's population, Li and his colleagues note.
Freshwater is extremely difficult to access for survival purposes in these dry regions, let alone to produce hydrogen fuel. Pollution, climate change, and factories that gobble up water only exacerbate water scarcity concerns.
And while desalination can free up seawater for hydrogen fuel production in coastal areas, this significantly increases the cost and complexity of the process.
"Most areas on Earth with high solar and wind potential lack freshwater," Li adds. "For example, a desert is deemed a good place for solar power, but has no fresh water."
What they did — Previously, Li researched ways to purify gases from smokestacks to capture the carbon dioxide within, so he got a handle on how to catch gases from the air. So when Li's research expanded to hydrogen production and the hunt for fresh water, reflecting on his past work gave way to a eureka moment.
To see if his concept would work in water-scarce, low-humidity regions, Li checked the relative air humidity in Alice Springs, an Australian town next to the famous Uluru Rock in the deep of the country’s central desert.
He observed that Alice Springs had an average relative humidity of 20 percent throughout the year. Since this was far more moisture than they needed, electrolysis from thin air was definitely possible — even in some of the harshest environments.
In their experiments, the researchers used renewable energy from solar and wind power to operate a device that could generate hydrogen fuel from water in the air with an efficiency of about 95 percent.
The device in question is made of porous, spongy material that can take in moisture from the air, sort of like the silica gel packets found in our beef jerky packaging. Then, electrodes at either end turn the molecules into hydrogen and oxygen.
"This work reported the first technology that can directly produce high-purity hydrogen from the air without using a liquid water feed," Li says. "This technology can potentially enable green hydrogen in areas suffering from water scarcity, such as Middle and West Asia, North Africa, Central Australia, and West America, which are also areas abundant in solar power."
Why it matters — In lab conditions, the new method could operate for more than 12 consecutive days and create hydrogen from the air with as little as 4 percent humidity in lab conditions. In comparison, in the drought-ridden Sahel region that spans east from Senegal to Eritrea, the average relative humidity is about 20 percent.
The scientists also tested their invention outside at the University of Melbourne campus, where temperatures varied from around 70 to 100 degrees Fahrenheit and the relative humidity ranged from 20 to 40 percent. On a warm sunny day, five modules that each had about 7.84 square centimeters of surface to yield hydrogen from the air could spawn 130 cubic feet of fuel per day.
The potential environmental impact of this device harvesting water from the air is likely negligible, Li notes. For instance, to supply hydrogen to all the residents and visitors at Alice Springs using the team’s technology, the relative humidity of the air in their surroundings would only fall by 0.02 percent.
What’s next — The scientists have just been offered venture capital cash to scale up their research. In the future, they aim to test a 107-square-foot version of their device in harsh environments, such as a desert, frozen zone, or stormy area, Li says.
Editor's note: On September 9, 2022, this post was updated to remove an editing error. The technology would likely not be viable on Mars.