A Plant‐Transpiration‐Process‐Inspired Strategy for Highly Efficient Solar Evaporation

Abstract

efficiency boosting of solar evaporation has become the forefront research interest in the area of solar energy conversion and applications. As water evaporation is an interfacial process, the localization of heat at the air-water interface by floating a photothermal material at the air-water interface, instead of heating the bulk water, has been considered to be the key of solar-evaporation acceleration. [13][14][15][16][17] However, solar evaporation by interfacial heat-localization involves the cooperation of sequential processes of sunlight absorbing/converting, heat localization, and water translocation. Accordingly, various self-floating double-layer materials consisting of a bottom water-pumping layer and a top light-absorbing layer have been deliberately designed to optimize/reconcile the above-described processes. [18][19][20][21][22][23][24][25][26] Complex/harsh fabrication processes (e.g., high temperature, freeze drying) and/or expensive raw materials (e.g., noble metals and graphene) are generally required to optimize the composite properties, which results in high cost and poor scalability for practical applications. Therefore, it is imperative to develop low-cost and scalable photothermal materials to meet the high-volume production of solar evaporation with further improved efficiency. Herein, inspired by the transpiration process and capillary action of natural plants, we developed a simple and low-cost strategy to make a photothermal material for solar evaporation by coating nature-produced wood with polydopamine (PDA) (main composition of melanin and adhesive protein of mussel). Both of the materials are cost effective, biodegradable, and environmentally friendly. The as-fabricated PDA-coated wood exhibits superior solar-steam generation efficiency compared to the previously reported materials for solar evaporation.In nature, the transpiration process of plants is associated with the interfacial evaporation of water on the leaves and the translocation of water from the underground to the leaf. [27] The evaporation on plant leaves creates a negative water vapor pressure, which triggers the pulling of water from root up to the leaf via capillary action. Inspired by this natural process extensively employed by plants, we hypothesized that naturally produced wood could be an excellent candidate for application in solar evaporation. Because of its lower density (compared to water) and capillary-induced superhydrophilic nature, wood can float on the water surface and translocate water from the bulk The conversion of solar energy into heat for solar steam generation is significant for energy saving and clean water supply. Recent advances in the design and application of photothermal-based water-evaporation systems have attracted intense research interest. However, it is imperative to develop a low-cost and scalable photothermal system with further improved energy conversion efficiency to meet the demand for real-world applications. Inspired by the natural transpiration process of plants, a wood-polyd...

Harnessing Solar‐Driven Photothermal Effect toward the Water–Energy Nexus

“…As a result, Chinese black ink as the solar absorber coating was required to be further stabilized by atomic layer deposition (ALD) technique to improve the interfacial adhesion to the substrate and prevent the ink dispersing into the water. [71] Beyond above report, a series of PDA coatings have been developed as the photothermal agents for various applications, including photothermal therapy, [101] photothermal antibacteria, [102] photothermal-assisted MD, [103] photo thermalassisted water evaporation, [104,105] and photothermal-assisted crude oil cleanup. [97][98][99] It is well known that the structure of PDA is similar to eumelanin in organism, and thus it would enable PDA coating with excellent light absorption ability.…”

“…[97][98][99] It is well known that the structure of PDA is similar to eumelanin in organism, and thus it would enable PDA coating with excellent light absorption ability. [71] Given the feature of highly conjugated and delocalized molecule structure, a flexible porphyrin organic framework was recently exploited and in situ grew on a diverse range of porous substrates as the solar absorber, exhibiting a high absorption efficiency of 95% over the wavelength range from 300 to 1300 nm. [71] Beyond above report, a series of PDA coatings have been developed as the photothermal agents for various applications, including photothermal therapy, [101] photothermal antibacteria, [102] photothermal-assisted MD, [103] photo thermalassisted water evaporation, [104,105] and photothermal-assisted crude oil cleanup.…”

“…[41,60,70,71,138] Thanks to this unique structure, woodbased evaporator exhibited a higher water evaporation rate (1.31 kg m −2 h −1 ) than that of porous membrane-based evaporator (0.75 kg m −2 h −1 ) under simulated 1 sun illumination. Theoretically, for the same thickness and channel size, the vertical channels possess much higher water transport rate than the tortuous channels, due to their shorter transport pathway and lower transport barrier.…”

Fast‐Growing Field of Interfacial Solar Steam Generation: Evolutional Materials, Engineered Architectures, and Synergistic Applications

“…Trees are reckoned as one category of the most common biomass materials, due to their excellent properties and special significance in scientific researches. By depositing polydopamine (PDA) on a treated pine wood sample, Xu's group prepared PDA‐coated wood as a ISSG device . The as‐obtained ISSG device has an evaporation efficiency of 87% under only one solar irradiation, and it could have promising potential in large‐scale production of steam, due to the facile availability of abundant PDA and pine wood in nature.…”

Solar vapor generation optimization of a carbon‐black/wood‐flour system with strength enhanced by polystyrene

“…Because of the low cost, natural mesoporous and sturdy structure, wood as the bottom layer has attracted much research interest recently . Many bi‐layer solar steam generation systems have already been built with woods as the bottom layer, such as the flame‐treated wood, plasmonic wood, wood‐graphene oxide composite, carbon‐wood, and polydopamine‐coated wood . Recently, taking the advantage of the surface‐carbonized longitudinal wood, Liu et al have achieved a high evaporation efficiency of about 89% under a 10‐sun irradiation .…”