MXene-decorated magnetic phase-change microcapsules for solar-driven continuous seawater desalination with easy salt accumulation elimination

[Display omitted] •We developed a novel solar-driven interfacial evaporator for continuous and efficient desalination.•The developed evaporator is based on the MXene-decorated magnetic phase-change microcapsules.•The microcapsules show high latent-heat capacity and high solar photothermal conversion efficiency.•The evaporator achieves an increase in evaporation mass under intermittent solar illumination.•This study offers an effective solution for salt acumination problem in seawater desalination. Solar-driven interfacial evaporators provide a powerful means for rapid wastewater purification and seawater desalination. However, there is still an immense challenge in interfacial evaporators with efficient energy utilization and long-term evaporation stability due to intermittent solar illumination and salt accumulation. To address these issues, we developed a novel type of interfacial evaporator based on the microencapsulated n-tetracosane and n-eicosane as twin phase-change material (PCM) cores with a SiO2/Fe3O4 composite shell along with a surface-coated polypyrrole layer and surface-decorated MXene nanosheets. The resultant microcapsules act as both a solar absorber and a latent-heat storage material for sustainable evaporation of seawater. Benefiting from a rational combination of PCMs and solar absorbers, the evaporator based on the microcapsules achieved a high light absorption efficiency of 95.4 % together with evaporation rates of 2.04 and 4.11 kg·m−2·h−1 under 1.0-sun and 2.0-sun illumination, respectively. Owing to the photothermal energy released by the PCM cores, the developed evaporator exhibits a consecutive and stable evaporation behavior even without solar illumination. Compared to conventional evaporators without a PCM, there is an increase by 0.45 kg·m−2 in the yield of the distilled water obtained from the developed evaporator under 2.0-sun illumination and then in the dark environment. Based on magnetic Fe3O4 nanoparticles in the silica-matrix shell, the separability of the microcapsules from the accumulated salt crystals was improved through simple washing and magnetic separation. Through an innovative integration of magnetic phase-change microcapsules and solar absorbers, this study will provide a new idea and promising approach for the sustainable evaporation system design based on solar energy utilization for applications of seawater desalination and wastewater treatment.