Water Skin Effect and Arched Double‐Sided Evaporation for Boosting All‐Weather High Salinity Desalination

Abstract

High efficiency, long‐term salt rejection, and continuous operation under all‐weather conditions have always been the goals of solar‐driven desalination of high salinity brine. Here, a synergistic strategy of water skin effect and double‐sided evaporation is proposed by an arched evaporator to overcome the above issues. Specifically, a hydrophobic carbon‐fiber cloth (CC) is coated with metal‐organic framework (MOF)‐derived superhydrophilic carbon films, and bent into an arch‐like configuration. Due to unique hydrophobic‐core/hydrophilic‐shell structure, an ultrathin water film (30–150 µm) is confined to the outer layer like skin. Thanks to the water skin effect and coevaporation of outer and inner surfaces, the arched evaporator displays ultrahigh evaporation rate of 3.21 kg m−2 h−1 (3.5 wt% NaCl) and 2.87 kg m−2 h−1 (20 wt% NaCl) under 1 sun illumination. Simultaneously, the free‐flowing water skin with fast convection for salt rejection, ensures stable evaporation performance during the whole day. Additionally, an evaporation rate up to 3.5 kg m−2 h−1 is acquired with only 2.5 V input voltage in a dark environment, attributable to the superior electrothermal effect of CC. The constructed evaporator with all‐in‐one function provides an effective way for commercial, portable photothermal conversion to achieve seawater purification.

Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

“…Wang et al bent hydrophobic carbon fiber cloth coated with MOFs into an arched structure. 326 Based on the above characteristics, the evaporation rate can reach 3.15, 3.06, and 2.83 kg m −2 h −1 under 1 kW m −2 solar radiation during desalination of 3.5, 10, and 15 wt% simulated seawater. Liang et.…”

Guar Gum-Based Macroporous Hygroscopic Polymer for Efficient Atmospheric Water Harvesting

“…Solar-driven atmospheric water harvesting technology (SAWH) provides a sustainable and environmentally friendly method to generate fresh water, regardless of geographical location . In recent years, the technology has received increasing attention from researchers aiming to address the increasingly severe global water scarcity crisis. − SAWH has been inspired by solar interface evaporation − and passive radiative cooling, − which has been rapidly developed. Its basic principle is to use hygroscopic materials to spontaneously collect atmosphere moisture and store it inside the materials, effectively use sunlight to generate heat and as a driving force to promote the release of water vapor in the hygroscopic material, and finally convert the water vapor into droplets through direct condensation or other technical means to complete the collection of atmosphere moisture. , With the rapid development of SAWH, it has been gradually applied to agricultural irrigation − and human life. , …”

3D Tea-Residue Microcrystalline Cellulose Aerogel with Aligned Channels for Solar-Driven Interfacial Evaporation Co-generation

“…However, this mode of power generation required the placement of materials on commercial thermoelectric modules, adding additional costs. 2,28,39 Subsequently, the salinity gradient effect 40 and the water skin effect, 41 hydrovoltaic effect, 42,43 power generation effect have also been favored by researchers. 44,45 Wu et al reported an efficient water evaporation-driven generator (rGO/CNT-EPG) utilizing the synergistic effect of a high water evaporation rate and electrical conductivity to achieve a spectacular continuous power output as high as 0.53 W m −2 and a high current density of 267 μA cm −2 under optimal conditions, and even in an outdoor environment, the rGO/CNT generator displayed a stable power density of 0.6 W m −2 with a high current density of 257.8 μA cm −2 through optical focusing, demonstrating its huge potential for practical applications.…”

“…Researchers have explored different modes of power generation initially in the form of single-stage thermoelectric power generation with the aid of commercial components, gradually evolving to multistage thermoelectric power generation. However, this mode of power generation required the placement of materials on commercial thermoelectric modules, adding additional costs. ,, Subsequently, the salinity gradient effect and the water skin effect, hydrovoltaic effect, , and mechanical power generation effect have also been favored by researchers. , Wu et al reported an efficient water evaporation-driven generator (rGO/CNT-EPG) utilizing the synergistic effect of a high water evaporation rate and electrical conductivity to achieve a spectacular continuous power output as high as 0.53 W m –2 and a high current density of 267 μA cm –2 under optimal conditions, and even in an outdoor environment, the rGO/CNT generator displayed a stable power density of 0.6 W m –2 with a high current density of 257.8 μA cm –2 through optical focusing, demonstrating its huge potential for practical applications . Mao et al designed an integrated photothermal solar steam generator utilizing electrospun PA66/CB NFs as a light absorber, whose unique unidirectional brine transport characteristic carefully achieves spatial segregation of the evaporation zone and the salt crystallization zone, resulting in the simultaneous formation of a constant salinity gradient for sustainable power generation with a salt collection rate of 0.055 kg m –2 h –1 under 1 sun in brine with a 3.5 wt % salinity and a 320 mV of complementary power generation .…”