Scientists successfully turned thin air into green hydrogen for 12 days

Last month, IE reported the grim side of lithium mining, as was revealed in pictures taken from the sky. Large stretches of salt flats in the Lithium Triangle of Argentina, Bolivia, and Chile are now covered with brine pumped to extract lithium, risking local flora, fauna, and communities.

The long-term solution to the problem may lie in other energy sources, such as hydrogen.

As green as it gets

Hydrogen combustion is possibly the cleanest of all energy resources we have on the planet. The fuel is relatively easy to transport and can be burnt anywhere to generate only water as the end product. Moreover, the water can be split back into hydrogen and oxygen using a renewable energy source to yield green hydrogen once again.

Scientists have been deploying water electrolyzers to split freshwater into a clean energy source, aiming to tie them up with renewable sources of power to make them greener and more sustainable. Unfortunately, that is precisely where the problem lies.

There is a strong mismatch between the availability of freshwater and renewable energy sources. Water is scarce even to meet local needs in regions where wind and solar are abundant. Renewables are scarce in areas with plenty of fresh water to make hydrogen fuel.

Tapping into the air's moisture

IE has previously reported how researchers want to tap into the moisture content in the air to solve water woes. A research collaboration of scientists from China, Australia, and the U.K. wants to take this a step forward and harvest green hydrogen from the system.

The researchers use a hygroscopic electrolyte to absorb the moisture from the air and then power the electrolysis using energy harnessed from the sun or wind. Their current density with their setup was 574mA per sq. cm. The prototype was operated consecutively for 12 days, during which the Faradaic efficiency was stable at 95 percent, the researchers said in a paper published today.

The researchers also tested their prototype in dry regions with a relative humidity of four percent and found that it performed satisfactorily in bone-dry environments. The technology used is scalable, and the researchers are confident that it could be used to provide green hydrogen fuel to arid, semi-arid, and remote regions of the world in a sustainable manner.

Abstract

Green hydrogen produced by water splitting using renewable energy is the most promising energy carrier of the low-carbon economy. However, the geographic mismatch between renewables distribution and freshwater availability poses a significant challenge to its production. Here, we demonstrate a method of direct hydrogen production from the air, namely, in situ capture of freshwater from the atmosphere using hygroscopic electrolytes and electrolysis powered by solar or wind with a current density up to 574 mA cm⁻². A prototype of such has been established and operated for 12 consecutive days with a stable performance at a Faradaic efficiency of around 95%. This so-called direct air electrolysis (DAE) module can work under a bone-dry environment with a relative humidity of 4%, overcoming water supply issues and producing green hydrogen sustainably with minimal impact to the environment. The DAE modules can be easily scaled to provide hydrogen to remote, (semi-) arid, and scattered areas.