Simultaneous Passive Water and Electricity Generation in Arid Regions via Fe³⁺/Li⁺ Cross-Linked Hygroscopic Hydrogels

Humans are confronting global water scarcity and energy shortages in data centers, and utilizing moisture from the air to address both water and electricity issues is a promising direction. Here, a porous hygroscopic hydrogel is integrated, which is composed of sodium alginate that is co-loaded with Fe³⁺ and Li⁺. Hydrophilic adsorption sites are constructed via ionic cross-linking and salt loading, enabling low desorption enthalpy (<40 kJ mol^{- 1}) for efficient water desorption. The water uptake of the dual-ionic hydrogel is over 5.1 g g^-1 at 90% RH, and this value is 1.1 g g^-1 at 30% RH. By designing a water harvesting device with rotating adsorption/desorption zones, with a daily production of 11.8 L kg_hydrogel ^-1 at 70% RH. The hydrogel not only provides abundant sites for moisture adsorption and storage but also offers channels for ion transport to enhance electricity generation. By constructing an asymmetric humidity structure, the dissociated cations in the hydrogel will diffusion to the substrate by concentration gradient and the electricity is evocated, producing a highly short-circuit current (250 µA) and open-circuit voltage (7.6 V), illuminating the multi-LED lights.