Solar-driven interfacial evaporation is an attractive method for seawater desalination, but the solid-salt crystallization on solar-absorber severely shelters sunlight and thus deteriorates the evaporation rate. To solve this problem, herein we have reported vertically symmetrical evaporator based on cotton-Cs_xWO₃ fabrics. Cs_xWO₃ nanorods have been prepared and then coated on cotton fabrics. The resulting cotton-Cs_xWO₃ fabrics exhibit broad UV-Vis-NIR photoabsorption from 200 to 2500 nm with solar absorbance efficiency of 90.5%. Subsequently, by coating two similar cotton-Cs_xWO₃ fabrics on double surfaces of a cotton-embedded polystyrene (PS) foam, vertically symmetrical evaporator has been designed and constructed. When the evaporator is floating on NaCl solution (3.5 wt%), cotton-Cs_xWO₃ fabric on top surface can absorb light under solar irradiation (1.0 kW m⁻²), conferring a high evaporation rate of 1.56 kg m⁻² h⁻¹ with an efficiency of 86.8%. When high-concentration (21 wt%) NaCl solution is used, the evaporation rate goes down from 1.52 to 0.53 kg m⁻² h⁻¹ within 8 h, due to the solid-salt crystallization on top surface. Importantly, the symmetrical evaporator can be self-cleaned by an inversion strategy (2 times h⁻¹), conferring high and stable rate (1.53–1.58 kg m⁻² h⁻¹) in the 20-h cycling evaporation and thus having great potential in the practical seawater desalination.

太阳能驱动的界面蒸发是海水淡化的一种有吸引力的方法，但是太阳能吸收器上的固体盐结晶会严重遮挡阳光，从而降低蒸发速度。为了解决这个问题，在此我们报道了基于棉-Cs _x WO ₃织物的垂直对称蒸发器。已经制备了Cs _x WO ₃纳米棒，然后将其涂覆在棉织物上。所得的棉-Cs _x WO ₃织物在200-2500 nm范围内表现出宽泛的UV-Vis-NIR光吸收，日光吸收效率为90.5％。随后，通过涂覆两个相似的棉-Cs _x WO ₃设计并制造了棉质嵌入聚苯乙烯（PS）泡沫双面表面上的织物，并设计了垂直对称的蒸发器。当蒸发器漂浮在NaCl溶液（3.5 wt％）上时，顶表面上的Cotton-Cs _x WO ₃织物可以在太阳辐射下（1.0 kW m ^-2）吸收光，从而赋予1.56 kg m ^-2  h的高蒸发速率^-1，效率为86.8％。当使用高浓度（21 wt％）NaCl溶液时，由于顶面上的固体盐结晶，蒸发速度在8小时内从1.52 kg m ^-2  h ^-1下降到0.53 kg m ^-2 h ^-1。重要的是，对称蒸发器可以通过反转策略进行自我清洁（2倍h^-1），在20小时循环蒸发中具有较高且稳定的速率（1.53-1.58 kg m ^-2  h ^-1），因此在实际的海水淡化中具有很大的潜力。