A solar-powered interfacial evaporation system based on MoS2-decorated magnetic phase-change microcapsules for sustainable seawater desalination

Abstract

A novel solar-powered interfacial evaporator based on MoS₂-decorated magnetic phase change microcapsules (hereafter named “MoS₂-MEPCM”) has been developed for sustainable seawater desalination. MoS₂-MEPCM was synthesized through encapsulating n-docosane as a phase change material core in an Fe₃O₄/SiO₂ composite shell, followed by coating a poly(3,4-ethylenedioxythiophene) (PEDOT) functional layer and then decorating MoS₂ nanosheets. The resultant microcapsules not only exhibit a high latent heat capacity of over 150 J g⁻¹, but also present a superior ability of broadband solar absorption and photothermal conversion thanks to a combination of the PEDOT functional layer and MoS₂ nanosheets as solar absorbents. This can drive the highly efficient and continuous interfacial evaporation of seawater or wastewater both under solar illumination and in a dark environment. The MoS₂-MEPCM-based evaporator developed in this study exhibits a high evaporation rate of 2.06 kg m⁻² h⁻¹ under an illumination intensity of 1.0 kW m⁻². Compared to the evaporator without an n-docosane core, the developed evaporator shows an increase in the water evaporation mass by 0.33 kg m⁻² under an illumination intensity of 1.0 kW m⁻² for 110 min and then holding in a dark environment for 110 min, and its total water production increases by 1.23 kg m⁻² under natural solar illumination for 10 h on a semi-cloudy day with unstable solar intensity. Moreover, the introduction of Fe₃O₄ nanoparticles into the capsule shell endows MoS₂-MEPCM with magnetic effectiveness. This simplifies its separability from acuminated salt crystals and facilitates its recyclability for long-term use in solar-driven seawater desalination and wastewater purification. This study offers a new approach for the design and development of a highly efficient solar-powered evaporation system for seawater desalination and wastewater purification under intermittent solar illumination.