Biomimetic All-Wood Sponge for the Co-Generation of Adsorption-Based Atmospheric Water Harvesting and Hydrovoltaic Power Generation

Atmospheric water harvesting (AWH) has garnered widespread attention for the alleviation of freshwater scarcity. However, AWH still presents challenges in simultaneously achieving rapid adsorption–desorption, low-energy regeneration, and environmentally sustainable development. Herein, a biomimetic all-biomass double-layer sponge is prepared to spatially separate moisture capture from solar-driven desorption while integrating hydrovoltaic power generation (HG) for the co-production of water and electricity. Inspired by tree transpiration, the carboxylated wood scaffold loaded with LiCl mimics root-like moisture uptake, while the recycled demethylated lignin coated on the upper layer serves as a photothermal evaporation layer that drives efficient solar-induced desorption analogous to leaf-mediated sunlight absorption. The biomimetic double-layer structure enables efficient moisture absorption and desorption, with vertical humidity gradients guiding water through directional fiber microchannels and generating sustained flow potentials. Under 60% relative humidity (RH), 25 °C, and 1-sun illumination, the open-circuit voltage ( V oc ) of the double-layer wood sponge is ~430 mV, with a short-circuit current ( I sc ) of ~6.3 μA and water uptake capacity of ~1.45 g g −1 , maintaining stable properties over multiple adsorption–desorption cycles. Under simulated conditions outdoors, freshwater can be effectively harvested, while the generated electricity can power lighting or be stored in capacitors to supply commercial electronic devices. In this strategy, the natural cellulose–lignin structure within wood is restructured and repurposed into a low-cost, sustainable platform that supplies both freshwater and environmental energy, providing a scalable pathway for efficient collection of water resources in resource-constrained regions.