Air has ‘natural inexhaustibility’ and there are 12.9trn tonnes of water in air at any moment, the study found.
Even in the world’s most challenging environments, such as the Sahel desert and Ayers Rock in Australia, the average relative humidity is about 20% and 21% respectively, the research states.
A solar-driven prototype with five parallel electrolysers has been devised to work in the open air, achieving an average hydrogen generation rate of 745 L H2 day−1 m−2 cathode; and a wind-driven prototype has also been demonstrated for hydrogen (H2) production from the air.
The study demonstrates a method of direct hydrogen production from the air, namely, in situ capture of freshwater from the atmosphere using hygroscopic electrolyte and electrolysis powered by solar or wind with a current density up to 574 mA cm−2.
A prototype has been established and operated for 12 consecutive days with a stable performance at a Faradaic efficiency around 95%.
“This work opens up a sustainable pathway to produce green hydrogen without consuming liquid water,” it concludes.
While H2 produced by water electrolysis using renewable energy, namely, the green hydrogen, represents the most promising energy carrier of the low-carbon economy, the deployment of water electrolyses are geographically constrained by the availability of freshwater.
Areas rich in renewable energies are commonly short in water supply. There is a geographic match between the shortage of freshwater and the potential of solar power and wind power, respectively, in the majority of the continents, such as North Africa, West, and Central Asia, Midwest Oceania, and southwest of North America.