Efficient and antifouling interfacial solar desalination guided by a transient salt capacitance model

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Interfacial solar desalination has been considered as a promising strategy to address the challenge of freshwater scarcity because of its high solar-to-vapor efficiency. However, the high evaporation rate would be restrained if salt crystallization occurs on the evaporation interface. Herein, we propose a capacitance model to describe transient heat transfer and salt rejecting processes during interfacial evaporation. This model allows us to identify the water layer thickness as a new design parameter. With the new understanding, the downward water channel ratio can be minimized to reduce heat loss without salt fouling. Experimental demonstrations show the high efficiency and long-term stability of our design using extremely low-cost and easily accessible materials. The maximum daily freshwater yield is as high as 6.0 kg/m2 under natural sunlight. Our findings not only address the challenge of salt fouling but also provide insights into transient processes during interfacial evaporation.