Design of interface-stable Janus solar-energy evaporator

Abstract

Solar-driven interfacial evaporation has been recognized as a promising and green strategy to solve the global fresh water crisis by promoting seawater desalination and sewage treatment. The high evaporative efficiency of evaporators has long been the focus in this field. However, it is rarely reported to enhance the interface stability of the solar steam generator, although it is of great value in simplifying devices and expanding application scenarios. Here, we design a novel approach to fabricate Janus solar-energy evaporator, inspired by the superhydrophobic/superhydrophilic binary cooperation strategy of lotus leaf. The upper superhydrophobic CNT@epoxy coating achieve floatability and high-efficient photothermal conversion, and the lower superhydrophilic SiO2 coating ensure efficient water transportation and evaporation heat localization. Using copper foam as a representative skeleton structure, we perform its unique advantages in interface stability and excellent evaporation. The results show that its maximum loading and stripping pressure are about 42.5 Pa and 37.2 Pa, and the evaporation rate can reach 1.84 kg m−2 h−1 under one solar illumination intensity. Further testing reveal that the ion rejection ratios are over 99.99% when treating simulated seawater, lake water or emulsified oil. These multiple key properties that have been integrated into our Janus solar-energy evaporator are expected to provide unique advantages for a wide range of applications in seawater desalination and sewage treatment.