Bioinspired bilayer hydrogel integrating atmospheric water harvesting with vapor-fed solar hydrogen production

Atmospheric water harvesting-driven photocatalytic hydrogen evolution promises decentralized fuel production in arid regions, but is can be constrained by sluggish vapor supply and limited interfacial water availability. Here, we report a bioinspired bilayer hydrogel that functionally integrates atmospheric moisture capture with vapor-fed photocatalytic H₂ evolution. The hygroscopic P(AcH)-LiCl layer captures, stores, and releases atmospheric water, while the photocatalytic Ag/TiO₂-P(HEA) layer provides photothermally heating and photocatalytic conversion. Under 90% RH, the device achieves an H₂ generation rate of 5.2 mmol m⁻² h⁻¹ together with 1.12 kg m⁻² of condensed water recovery in the same closed reactor. The correlation between water release and H₂ generation, together with multiphysics simulations, indicates that the bilayer architecture facilitates water release and helps maintain interfacial water availability under irradiation. Density functional theory calculations further indicate that the vapor-fed environment may facilitate H* adsorption on Ag/TiO₂. This work presents a functional bilayer hydrogel platform that integrates atmospheric water harvesting with vapor-fed photocatalytic H₂ production, providing a potential strategy for solar-driven water utilization.