Design of MoS2/MMT bi-layered aerogels integrated with phase change materials for sustained and efficient solar desalination

Abstract

Solar desalination is a promising technology which can produce drinkable water from seawater or wastewater driven by solar energy. However, the intermittency of the sun restricts the evaporation rate and freshwater output yield. Here, in order to promote solar energy utilization efficiency and freshwater yield, phase change materials used as solar thermal energy storing materials are introduced into the solar evaporators. The designed solar evaporator has a double layer aerogel structure, in which the bottom layer is constructed by montmorillonite (MMT) aerogel with a function of water supply and thermal insulation. At the same time, the upper layer aerogel, which are constructed by MoS2 and paraffin@SiO2 phase change microcapsules, plays the role of solar energy harvesting, storage and solar steam generation. In this strategy, the phase change microcapsules with a latent heat of 177.85 J/g enables the solar evaporator to store solar thermal energy during illumination, and to release heat for continuous seawater desalination when there is no sunlight. Results show that MoS2/MMT solar evaporator achieves a water evaporation rate of 1.32 kg·m−2·h−1 and an evaporation efficiency of 86.22 % at a light intensity of 1 kW·m−2. When there is no sunlight, the evaporation rate and evaporation efficiency are still as high as 0.71 kg·m−2·h−1 and 44.36 % even after 20 min running, which greatly promotes the solar energy utilization efficiency and freshwater yield. In addition, the solar evaporator can produce high-quality fresh water with 99.9 % salt ions removal. Through the integration of phase change materials, the solar evaporator enables sustained and efficient solar desalination regardless of solar intermittency, resulting to great promising future in the large-scale freshwater production.