Solar Desalination via Multilayers of Transparent Photothermal Fe₃O₄@Cu_2–<i>x</i>S Thin Films

Abstract

In contrast to a conventional single layer solar still, herein a multilayer system for solar light harvesting and water evaporation via transparent photothermal thin films is developed. Monodispersed Fe 3 O 4 @Cu 2– x S nanoparticles are dispersed in a polymer solution and deposited on glass and quartz substrates as transparent thin films. These thin films are optically characterized with strong absorptions in the UV and NIR regions, and high average visible transmittance. The photon energies in the UV/NIR regions are converted to heat increasing the water evaporation rate, while the film high transparency makes it possible for light to pass through many layers for an enlarged solar harvesting surface area. A multilayer photothermal evaporation system (MPTES) is developed for water evaporation experiments using various photothermal films. Water evaporation rates are compared between Fe 3 O 4 @Cu 2– x S and Fe 3 O 4 against different numbers of layers in the MPTES. The photothermal and optical properties of Fe 3 O 4 @Cu 2– x S thin films are correlated to the heating behaviors and saltwater evaporation rate. Due to high transparency and strong photothermal effects of the films, water evaporation is significantly enhanced via multilayers. The concept of the multilayer solar still will show promise in water desalination.