All Biomass‐Based Solar‐Driven Interfacial Evaporator for Efficient Seawater Desalination and Power Generation

Solar-driven interfacial evaporation has emerged as a promising strategy to alleviate global water scarcity. However, most existing evaporators still depend on synthetic materials, raising concerns over their environmental impact. Herein, Fe³⁺-coordination-driven assembly of cellulose nanofiber (CNF)/Fe³⁺/lignosulfonate (LS) into photothermal layer (CFL) with a porous CNF/Fe³⁺ aerogel (CF) water transport channe, respectively, to construct a fully biomass-derived solar-driven interfacial evaporator. The results establish that Fe³⁺-LS coordination synergistically endows with the outstanding photothermal performance of the CFL hydrogel, achieving 95% full-spectrum solar absorption. The hydrated polymer network present in the CFL hydrogel can regulate the molecular state of water, effectively lowering its vaporization enthalpy while maintaining rapid water transport. Based on these advantages, the system achieves an evaporation rate of 1.91 kg m^{- 2} h^-1 under 1 sun. The fully biomass-based evaporator can remove ≈96.6% of major metal ions (Na⁺, K⁺, Ca²⁺, Mg²⁺) from seawater to generate fresh water, exhibiting superior salt resistance and durability. Notably, CFL hydrogels integrated with a thermoelectric module achieve an open circuit voltage of 110 mV, enabling direct operation of a commercial fan. This work develops an environmentally benign and cost-efficient strategy employing a fully biomass-derived hydrogel evaporator from renewable plant-based bioploymers for sustainable seawater desalination.