An atmospheric water electrolyzer for decentralized green hydrogen production

The necessity of ultrapure water and water-transport infrastructure pose grand challenges in renewable-energy-assisted water electrolysis to produce green hydrogen. Directly accessing atmospheric water should offer a decisive solution because it provides ∼13 trillion kiloliters of pure water at any given instant. We show that the central challenge for atmospheric water electrolysis is related to the water-sorption kinetics of the proton-conducting membrane where state-of-the-art membranes critically fail. A proof-of-concept atmospheric water electrolyzer is demonstrated with a graphene oxide proton-conducting membrane, which has nearly three times higher water-sorption kinetics and ten times higher hydration number than a Nafion membrane due to capillary water condensation and the abundant presence of hydrophilic functionalities. At a wind velocity of ∼50 km/h, this electrolyzer delivers nearly 18 mL/h/cm² of green hydrogen directly from the feedstock of atmospheric water. Because this electrolyzer does not require water-transport infrastructure, it can be placed almost anywhere, which offers opportunities for decentralized green hydrogen production.