Salting‐Out Engineered Sulfonated Cellulosic Hydrogel with Proton Hopping Pathways for Integrated Water Purification and Electricity Generation

Interfacial solar evaporators capable of cogenerating clean water and electricity offer a promising solution to the water-energy nexus, yet large-scale implementation remains limited by expensive materials and energy-intensive fabrication. Here, we present a bio-derived, low-cost, and scalable sulfonated delignified biomass hydrogel (SSH) with a salting-out structured architecture that integrates solar-driven interfacial evaporation and hydrovoltaic power generation. The SSH, constructed from sulfonated delignified biomass, LDH@MXene photothermal fillers, and poly(vinyl alcohol), undergoes salting-out according to the Hofmeister effect to form stabilized porous channels with tunable interchannel spacing. This architecture confines heat near the air-water interface and promotes directional water transport, enabling a high evaporation rate. The dense sulfonate-rich anionic network and reinforced hydrogen-bonding matrix facilitate efficient proton hopping, delivering an open-circuit voltage of 784 mV and short-circuit current of 82.14 µA. Scaled SSH arrays demonstrate stable outdoor operation and sufficient output for self-powered sensing and continuous plant growth. Using trained predictive models, we estimate the annual water evaporation and hydrovoltaic performance of the SSH systems across diverse climatic conditions. This platform offers an energy-efficient and broadly deployable strategy for solar-driven clean water production and decentralized electricity generation, enabled by a sustainable, bio-derived materials platform, suited for resource-scarce regions.