hydrogen, [2] solar power plants, [3] photovoltaic cells, [4] photocatalysis, [5] and water desalination, [6] the photothermal materials based solar water evaporation is one of the most promising approaches for harvesting and conversion of solar energy. Solar vapor generation, more specifically, is a surface water evaporation process in which the light is absorbed and converted to heat energy by photothermal materials to generate vapor. Compared with the common water evaporation by solar radiation as heat source which suffers from the drawback of low solar energy conversion efficiency due to the fact that the part solar energy is converted to heat bulk water or is lost to the external environment, solar vapor generation based on photothermal materials has great advantages for its high light-to-heat conversion efficiency due to the fact that solar radiation is only harvested and located at the water-air interface to heat thin air-water surface layer that can effectively minimize the heat loss. [7] Based on the merits mentioned above, up to now, the solar steam generator has been emerged as a kind of efficient device for harvesting solar energy and attracted extensively much more attention in both industrial and academic research throughout the past decades. [8,9] In a given solar steam generation system, the photothermal materials is essential. A desired photothermal material should meet the following criteria: the broadband sunlight absorbability, low thermal conductivity, open porosity for rapid water molecules transportation, and high-energy conversion efficiency. [10,11] Understanding of these complementary roles of these parameters for photothermal material, so far, a number of photothermal materials, including carbon-based materials, [7,8,[12][13][14] metallic nanoparticles, [15][16][17] biomass-based materials, [18,19] and porous polymers, [20,21] etc., have been developed to use as efficient solar steam generators.In general, porous materials with bilayer structure are widely adapted as solar steam generator, in which the top layer consists of carbon materials for light absorption (e.g., graphene, [13] CNTs, [14] graphite, [7] etc.) while the bottom layer is composed by the porous materials (e.g., wood, [18] silica, [10] etc.) for Solar steam generation has been proven to be one of the most efficient approaches for harvesting solar energy for diverse applications such as distillation, desalination, and production of freshwater. Here, the synthesis of monolithic carbon aerogels by facile carbonization of conjugated microporous polymer nanotubes as efficient solar steam generators is reported. The monolithic carbon-aerogel networks consist of randomly aggregated hollow-carbon-nanotubes (HCNTs) with 100-250 nm in diameter and a length of up to several micrometers to form a hierarchically nanoporous network structure. Treatment of the HCNTs aerogels with an ammonium peroxydisulfate/sulfuric acid solution endows their superhydrophilic wettability which is beneficial for rapid transportation of water molecules. ...
We report the synthesis of elastomeric conjugated microporous polymer nanotube aerogels with exceptional mechanical strength, excellent porous features and low thermal conductivity, which show great potential for solar steam generation.
Solar steam generation is a highly promising technology for harvesting solar energy and desalination. Here, a new solar steam generation system is introduced based on a surface‐modified polyurethane sponge with bilayered structures for efficient solar steam generation. The top layer, coated with polydimethylsiloxane‐modified graphite powder, serves as light‐to‐heat conversion layer with a broad optical absorption, whereas the lower part of the sponge acts as a thermal insulator with a low thermal conductivity in the wet state (0.13882 W m−1 K−1). In addition, the strong hydrophobic wettability of the top layer (water contact angle: 148°) enables self‐floating behavior on water, which is beneficial for practical applications. The results show that compared with a silver‐nanoparticle‐doped sponge and an acid‐etched sponge doped with silver nanoparticles the graphite‐modified sponge (GS) exhibits the highest evaporation efficiency of 73.3 % under 1 kW m2 irradiation, which is 2.6 times that of pure water and far higher than that of untreated polyurethane sponge (36.0 %). The GS shows excellent stability, and its evaporation efficiency remains unchanged even after immersion in water for one month. Based on its cost‐efficient, simple, and scalable manufacturing process, excellent mechanical stability, and high recyclability, the GS shows great potential as an efficient photothermal material for a wide range of large‐scale applications such as solar steam generation, light absorption, heat localization, and seawater desalination.
Direct solar desalination with excellent solar photothermal efficiency, lower cost, and extended generator device lifetime is beneficial to increase potable water supplies. To address fundamental challenges in direct solar desalination, herein, we present a new and facile method for the scalable fabrication of the polymer porous foam (VMP) as salt-resistant photothermal materials, which was synthesized through a one-step hydrothermal method using styrene and 1-vinyl-3-ethylimidazolium tetrafluoroborate as monomers and N,N′-methylenebisacrylamide as the cross-linking agent. The as-resulted VMP shows excellent mechanical properties which could have a compression strain of 30%, resulting in its superior processability for practical operation. In addition, by taking advantage of its inherent low density, well-controlled porous structure (porosity is 73.81%), and extremely low thermal conductivity (0.03204 W m–1 K–1), the VMP exhibits an excellent solar evaporation property, and the solar photothermal efficiency can reach more than 88% under 1 kW m–2 irradiation. Moreover, the introduction of ionic liquid moiety (imidazolium tetrafluoroborate) into VMP results in its interesting superhydrophilic wettability, which can accelerate water transportation (wetting in 5s) and resolve the crystalline salt within 1.13 h. In addition, the interconnected macropores of the VMP, as water channels, can replenish the vaporized brine on the surface to prevent salt from adhering. The VMP shows a salt-resistant performance, for example, its solar evaporation efficiency remains nearly unchanged after 6 h duration under 1 sun irradiation. Based on its simple and cost-effective manufacturing process, excellent solar photothermal efficiency, and salt resistance, our VMP may be a promising candidate as photothermal materials for practical desalination from seawater and other wastewater.
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