Localized solar photothermal heating via plasmonic interfaces for high-efficiency water evaporation

Abstract

Photothermal conversion for interfacial solar water evaporation is a promising green energy technology for effective wastewater purification. In the current work, we report the fabrication of a novel interfacial evaporator system based on plasmonic nanoparticles (X-NPs = Ag, Ni, Co, and Cu) as efficient photothermal conversion agents, supported on a microporous Whatman membrane (MPM). A simple, low-cost, and green chemistry synthesis approach was employed to synthesize the Ag, Ni, Co, and Cu nanoparticles through thermal decomposition, using casein as a natural reducing and stabilizing agent. The resulting nanoparticles were uniformly coated on the porous structure of an MPM to fabricate stable and reproducible X-NPs@MPM evaporators. These interfacial evaporators exhibited high optical absorption and efficient light-to-heat conversion capabilities. Under solar irradiation (1.05 kW m⁻²), these systems achieved excellent photothermal conversion efficiencies of 96% (Ag), 92% (Ni), 86% (Co), and 82% (Cu). In addition to their high performance, the X-NPs@MPM evaporators are flexible, reusable, and easily engineered, demonstrating excellent potential for scalable solar vapour generation and sustainable water treatment applications.