Scientists pull hydrogen from thin air in promising clean energy move

Could replace fossil fuels in several energy-hungry industries in hot climates without water use

Scientists have produced hydrogen from thin air, a development they say could help industry harvest the promising eco-fuel in the most arid environments.

Hydrogen is being put forward as a replacement for fossil fuels in situations where electricity may be unsuitable, namely shipping, air transport, and industries such as steel production.

While proposals for creating pure hydrogen from renewable electricity via electrolysis seem attractive to those trying to decarbonize the economy, the transition still needs water (a compound of hydrogen and oxygen) which can be scarce where solar electricity is abundant.

To avoid taking water from an already strained local supply, a team led by Gang Kevin Li, senior lecturer at the University of Melbourne, Australia, has built a system which extracts water from airborne vapor using a hygroscopic electrolyte, in this case sulfuric acid. The approach then uses solar-generated electricity to split the water into hydrogen and oxygen.

The team proved it could operate at a relative humidity of about 4 percent, well below that of most deserts. On a warm sunny day, the meter-square unit was able to produce 3.7m3 of hydrogen.

"Hydrogen is the ultimate clean energy," the paper, published in Nature Communications, said. "Despite being the most abundant element in the universe, hydrogen exists on the earth mainly in compounds like water. H2 produced by water electrolysis using renewable energy, namely, green hydrogen, represents the most promising energy carrier of the low-carbon economy. H2 can also be used as a medium of energy storage for intermittent energies such as solar, wind, and tidal."

The researchers pointed out that more than a third of the earth's land surface is arid or semi-arid, supporting 20 percent of the world's population, where freshwater is extremely difficult to access for daily life, let alone electrolysis. Pollution, industrial consumption, and global warming have added to water stress, they said.

Government and climate campaigners have proposed hydrogen as an alternative to fossil fuels, but the vast majority of industrial hydrogen is still extracted from natural gas [PDF] in a process that releases greenhouse gasses and requires energy, which often comes from carbon fuels. Only 1 percent of US hydrogen comes from electrolysis [PDF].

Li has argued that the team's technology could easily scale and complement existing electrolysis systems, which have their own problems. The complexity of current system designs create high capital costs for hydrogen electrolysis, although lower cost alternatives have been proposed.

Investment in green hydrogen has had a fillip in recent years. In the US, a $9.5 billion investment is part of president Joe Biden's $1.2 trillion Infrastructure Investment and Jobs Act. The UK launched its hydrogen strategy in August 2021, claiming production could be worth £13 billion ($14.8 billion) to the economy by 2050. The EU hydrogen strategy was adopted in July 2020, creating the European Clean Hydrogen Alliance. Over in Germany, hydrogen fuel cell passenger trains have now gone into operation.

But it is not just hydrogen researchers hope to pluck from thin air. Last month, the Swiss Federal Institute of Technology (ETH) reported a technique which promises the extraction of hydrocarbon fuels too. ®

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