Wu Shenghao, Gong Biyao, Yang Huachao, Tian Yikuan, Xu Chenxuan, Guo Xinzheng, Xiong Guoping, Luo Tengfei, Yan Jianhua, Cen Kefa, Bo Zheng, Ostrikov Kostya Ken, Fisher Timothy S
State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China.
Department of Mechanical & Aerospace Engineering and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
ACS Appl Mater Interfaces. 2020 Aug 26;12(34):38512-38521. doi: 10.1021/acsami.0c07921. Epub 2020 Aug 14.
Solar desalination that exploits interfacial evaporation represents a promising solution to global water scarcity. Real-world feedstocks (., natural seawater and contaminated water) include oil contamination issues, raising a compelling need for desalination systems that offer anti-oil-fouling capability; however, it is still challenging to prepare oil-repellent and meanwhile water-attracting surfaces. This work demonstrates a concept of molecularly dispersing functional F and Na sites on plasma-made vertically oriented graphene nanosheets to achieve an in-air and in-water oleophobic, hydrophilic surface. The graphene architecture presents high in-air (138°) and in-water (145°) oil contact angles, with simultaneously high water affinity (0°). Such surface wettability is enabled by oleophobic, hydrophobic -CF, and hydrophilic -COONa groups of the molecules that disperse on graphene surfaces; low-dispersion (0.439 mJ m) and high-polarity (95.199 mJ m) components of the solid surface tension; and increased surface roughness produced by graphene edges. The graphene nanostructures pump water upward by capillary action but repel oil from the surface, leading to complete in-water and in-air oil rejection and universal anti-oil-fouling capability for solar desalination. Consequently, stable solar-vapor energy efficiency of more than 85% is achieved regardless of whether the feedstock is pure or oil-contaminated water (., a mixture of oil floating on water, an oil-in-water emulsion), resulting in the efficient production of clean water over several days. This outstanding performance is attributed to the universal (both in-water and in-air) oleophobic wettability, together with high light absorptance contributed by nanotraps, fast interfacial heat transfer enhanced by finlike nanostructures, and accelerated evaporation enabled by sharp graphene edges.
利用界面蒸发的太阳能海水淡化是解决全球水资源短缺的一个有前景的方案。实际应用中的原料（如天然海水和污水）存在油污问题，因此迫切需要具备抗油污能力的海水淡化系统；然而，制备拒油同时又亲水的表面仍然具有挑战性。这项工作展示了一种概念，即将功能性的F和Na位点分子分散在等离子体制备的垂直取向石墨烯纳米片上，以实现空气中和水中均具有疏油、亲水性的表面。该石墨烯结构在空气中（138°）和水中（145°）均具有高油接触角，同时具有高水亲和力（0°）。这种表面润湿性是由分散在石墨烯表面的分子的疏油、疏水的-CF基团和亲水的-COONa基团实现的；固体表面张力的低分散（0.439 mJ/m）和高极性（95.199 mJ/m）成分；以及石墨烯边缘产生的表面粗糙度增加。石墨烯纳米结构通过毛细作用将水向上泵送，但将油从表面排斥，从而实现完全的水中和空气中的拒油以及太阳能海水淡化的通用抗油污能力。因此，无论原料是纯水还是受油污染的水（如浮在水上的油、水包油乳液的混合物），都能实现超过85%的稳定太阳能蒸汽能量效率，从而在数天内高效生产出清洁水。这种优异的性能归因于通用的（水中和空气中）疏油润湿性，以及纳米陷阱贡献的高吸光率、鳍状纳米结构增强的快速界面热传递和尖锐石墨烯边缘实现的加速蒸发。
