All-Biomass-Based Solar Steam Generator with Deep Eutectic Solvent Lignin Porous Carbon/Silver Nanoparticle Coatings for Efficient Water Evaporation

Solar-driven interfacial evaporation exhibits tremendous potential to address the challenge of freshwater scarcity. However, the low evaporation rate and high fabrication cost of petroleum-based materials hindered its advancement. This work proposes a programmed design of a bilayer evaporator using wood biomass and the emerging deep eutectic solvent technical lignin (DES lignin). The mild delignification process decreased its thermal conductivity (from 0.20 to 0.16 W m–1 K–1), while the DES lignin-derived porous carbon was used as the surface photothermal coating layer for light absorption. The results indicated that the increased surface area of lignin porous carbons can regulate the solar-derived evaporation rate. The DES lignin-derived porous carbons, equipped with abundant hydroxyl groups and enhanced photothermal conversion capability, enable in situ thermal reduction and loading of silver nanoparticles, which further endowed them with antibacterial functionality. The prepared evaporation device exhibited an excellent evaporation rate of 2.89 kg m–2 h–1 under 1.0 kW m–2. It was feasible for various wastewater treatments such as high-salinity wastewater, dye wastewater, and drilling wastewater with considerable stability and antibacterial performance. This work presents a facile technique for sustainable evaporator fabrication using wood and DES lignin, which also provides useful information for technical lignin valorization that results from the current emerging lignocellulose biorefinery process.