Scalable hydrogen production by harvesting moisture from the air under natural sunlight

Photocatalytic hydrogen production from solar energy is considered as one of the most cost-effective approaches to carbon neutrality. However, the geographic mismatch between liquid water and solar resources poses great challenges to its large-scale and low-cost practical application. An ingenious water self-replenishing photocatalytic system consisting of a porous photocatalytic layer with Pt/TiO 2 as catalyst and a hygroscopic hydrogel is reported herein. The hygroscopic hydrogel can harvest moisture from the atmosphere in dark and provide sufficient vapor for hydrogen production in porous photocatalytic layer under solar irradiation, ensuring a hydrogen production of 21.67 mmol m −2 h −1 . A large-scale prototype with reaction area of 24 cm × 24 cm demonstrates a stable H 2 production of 3673.9 mL m −2 day −1 under natural sunlight and is regenerated by atmospheric water harvesting at night. This work provides a new strategy for large-scale hydrogen production from the gaseous water in the air.