Direct Green Hydrogen Production from Nontraditional Water Sources Using a Water Vapor Electrolyzer with Hydrogel Composite Electrocatalysts

Directly using ubiquitous nontraditional water sources enhances the flexibility of a decentralized hydrogen (H₂) economy with surplus renewable electricity through water electrolysis. Side reactions and corrosion from impurities severely limit the water electrolysis systems’ lifetime unless water is pretreated. Here we demonstrate a strategy for direct H₂production from nontraditional water sources. The key advances for this water vapor electrolysis system (WVES) were integrating in situ water purification through water vapor generation and enhancing water vapor mass transfer through a composited hydrogel. The WVES achieved a current up to 500 mA cm^–2, with stability for over 60 h at 150 mA cm^–2. Sustained H₂production was demonstrated using synthetic saline water and natural nontraditional water sources. Economic and life cycle analyses indicated that the WVES reduces the levelized cost of hydrogen (LCOH) compared to conventional centralized PEM electrolyzers by 4.5–6.5 USD kg^–1and CO₂emissions by 0.29 kg CO₂-eq kg H₂^–1, demonstrating the potential of directly utilizing nontraditional water sources through WVES for decentralized H₂production.