Advanced Nanomaterials for Solar Vapor Generation and Desalination

Abstract

Solar vapor generation, one of the most efficient ways to use solar energy today, has recently received significant attention. Low-cost, environmentally friendly, and high-efficiency solar absorbers are highly desirable for use in practical applications of solar vapor generation, and it is currently impossible to achieve this. Sunlight-driven seawater evaporation is typically carried out on floating evaporators; however, the performance is severely limited by high evaporation enthalpy and reduced evaporation rate. Moreover, water evaporation requires a huge amount of thermal energy to eliminate the binding force of hydrogen bonds resulting from the hydrogen bonding of the surface water molecules and the bulk water molecules, which results in a high evaporation enthalpy 2444 kJ.kg-1, at 373.15 K at 1 atm, and limits further improvement of evaporation rate. Until recently, some porous materials, such as hydrogels and carbon foams, have been proven to have a lower enthalpy of evaporation of water than other porous materials. The types of low-enthalpy materials are limited, and further investigation is needed to fully understand the mechanism. Therefore, to reduce the evaporation enthalpy and avoid incline-induced reductions in evaporation, it is still necessary to design and develop evaporation devices that incorporate porous photothermal fabrics. The light-absorbing material in this study is a three-dimensional plasmonic covellite copper sulfide (CuS) hierarchical nanostructure created using the facile solvothermal process. As a result of the disorganization of hydrogen bonds on its surface, copper sulfide offers lower water evaporation enthalpy than pure water. Our material sample is further improved by incorporating Mo-based compounds into CuS. Consequently, the incorporation of Mo-based compounds into our synthesized CuS resulted in enhanced evaporation rates. the flower structure of CuS-Mo shows excellent evaporation performance because the flower-shaped structure increased the light-receiving area and water evaporation area. An efficient and broad spectrum of light absorption has been achieved for wavelengths of 400−700 nm, the visible range of solar light. A solar-driven evaporation setup has been designed and quantified under one sun by placing the sample membrane on a substrate that absorbs the salty water to evaluate the evaporation rate. The membrane containing our samples absorbs sunlight and converts it to heat, evaporating the salted water and leading us to the freshwater. The evaporation rate for the CuS was 2.87 Kg.m-2.h-1 under one sun (solar intensity 1.0 kW m−2), while with the enhanced CuS-Mo membrane, the evaporation rate increased to 3.14 Kg.m-2.h-1 under one sun.