A flexible thin-film membrane with broadband Ag@TiO₂ nanoparticle for high-efficiency solar evaporation enhancement

Harvesting solar energy for steam generation has been widely applied in processes, such as sterilization, water purification, sea water desalination, and electricity generation. It has been found that a nanoparticle-modified membrane (NPM) can directly convert incoming solar energy into thermal energy in a short time period. In this work, broadband core–shell Ag@TiO₂ nanoparticles (NPs) having significant larger absorbance were synthesized. Flexible membranes using the deposition of the synthesized NPs were fabricated and floated on the surface of water to enhance the water evaporation. The effects of the density of deposited NPs and the solar irradiance on the evaporation performance were systematically investigated. Results showed that under 5 sun (1 sun = 1 kW/m²) irradiation, the NPM obtained the highest evaporation capacity together with a considerable evaporation efficiency (52.7%) for NPs deposition of 1.0 g/m². In addition, an evaporative efficiency of up to 68.6% was attained under the solar irradiance of 1 sun. On the other hand, most of the heat lost was transferred into the bulk water and gave rise to the enhancement of sensible heat energy, which can be further used in a volumetric absorption type solar collector. - Highlights: • Flexible membrane with broadband Ag@TiO₂ nanoparticle was fabricated. • Steam generation properties of the nanoparticle membrane were systematically studied. • Only 1.0 g/m² of particles is required to obtain the maximum evaporation efficiency. • An evaporation efficiency of 69.2% was obtained under 1 sun illumination. • The high evaporation performance was the result of localized heating.