Corrugated Janus hydrogel-based solar evaporator with enhanced light-trapping nanostructures inspired by corn bracts for efficient seawater desalination

Solar desalination technology, with its green and sustainable characteristics, has become an effective solution to the problem of global freshwater shortage. However, conventional solar evaporators (SE) focus mainly on issues such as reducing the enthalpy of water evaporation and conduction heat loss. Thus, the light refraction losses caused by the surface structure under direct sunlight are neglected. In this study, inspired by corn bracts, a Janus-type SE (SWPP@PCM) with light-trapping effect was designed. By optimizing the SE surface design, the light refraction loss was significantly reduced and the light trapping capability was enhanced. The upper layer of SWPP@PCM consists of superhydrophobic wave polyurethane foam containing polypyrrole. The lower layer is a superhydrophilic hydrogel, consisting of polyvinyl alcohol, chitosan and aminated multiwall carbon nanotubes. The superhydrophobic layer reduces water droplet adhesion and promotes water vapor evaporation. The hydrophilic layer reduces the enthalpy of evaporation and accelerates water transport. Experimental results show that the evaporation rate of the SWPP@PCM solar evaporator reaches up to 3.81 kg·m −2 ·h −1 , and the evaporation efficiency under a single sunlight exposure can reach 96.21 %. Therefore, this 3D Janus self-floating SE (SWPP@PCM) with a light-trapping effect exhibits broad application potential in the fields of seawater desalination and wastewater purification.