Sustainable solar-powered seawater desalination enabled by phosphorene-decorated watermelon-like phase-change microcapsules

Solar-powered interfacial evaporation is considered as an emerging innovative technology for seawater desalination; however, it suffers from insufficient evaporation efficiency under intermittent solar irradiation. Aiming at realizing sustainable solar-powered seawater desalination for clean water production, we have designed a new type of watermelon-like phase-change microcapsules as a photothermal absorbent material for solar interfacial evaporators. This type of phase-change microcapsules was prepared through rational layer-by-layer microencapsulation with a ZrO 2 nanoparticle-containing n -docosane core as a phase-change material (PCM) for solar photothermal harvest and prompt thermal response, a ZrO 2 shell for the leakage prevention of the molten n -docosane core, and a polydopamine coating layer together with its surface-decorated phosphorene nanoflakes for high-efficient sunlight absorption and fast water transportation. The resultant microcapsules are featured by a watermelon-like microstructure as confirmed by transmission electron and scanning electron microscopy. They also exhibit a high light absorption efficiency of 84.95 %, a high latent heat capacity of 146.2 J g −1 , and good wettability. Equipped with the watermelon-like phase-change microcapsules, the developed solar interfacial evaporator obtained an evaporation rate of 3.09 kg m −2  h −1 under one-sun illumination for seawater desalination. The PCM core within the microcapsules can store solar photothermal energy as latent heat under sufficient solar irradiation and then release it under evaporation conditions without sunlight illumination, thus enhancing the water evaporation efficiency. This enables the developed evaporator to increase its total evaporation mass by 31.5 % on a cloudy day in comparison with the conversional solar evaporator without a PCM, indicating a remarkable enhancement in the evaporation performance under intermittent solar irradiation. The developed solar interfacial evaporator exhibits great potential for application in sustainable solar-powered seawater desalination.