Lignin-Based PVA Acetal Sponge Evaporator for Efficient Seawater Desalination and Power Generation

Combining solar-driven interfacial evaporation (SDIE) with hydrovoltaic electricity generation offers a promising route for concurrent fresh water and electricity production. However, existing systems often face challenges in achieving high evaporation rates, substantial power output, and mechanical durability concurrently. To address issues such as high evaporation enthalpy, low surface charge density in pores, and insufficient structural stability in evaporators, this study presents a lignin-based PSC porous sponge evaporator fabricated through facile foaming and aldehyde cross-linking. The incorporation of lignin imparts a hierarchical porous structure and functional properties, enabling efficient water-electricity cogeneration. The evaporator employs a polyvinyl alcohol (PVA) acetal network as the main framework, constructing continuous hydrophilic pathways. Additionally, sodium lignosulfonate (SLS) and sodium carboxymethyl cellulose (CMC) are introduced to form a high surface charge density network (Zeta potential reaching −41.2   mV) within the pores, promoting ion transport to enhance power output. Moreover, the hydrogen-bonding structure of water molecules is modulated by abundant hydrophilic functional groups within the system, which effectively lowers the evaporation enthalpy (~774   kJ   kg⁻¹) and thus enhances both evaporation and power generation performance. As shown by experimental results, under 1 sun illumination, the PSC sponge evaporator attains an evaporation rate of 4.38   kg   m⁻² h⁻¹. When tested in 3.5   wt% saline water, it still sustains an evaporation rate of 4.05   kg   m⁻² h⁻¹ and concurrently produces a voltage output of 0.397   V. Further modular device integration verifies the feasibility of continuous freshwater collection and electricity storage capable of powering an LED. The study puts forward a novel material design strategy for constructing low-cost, environmentally friendly, and sustainable interfacial evaporators for water-electricity cogeneration.