Preparation Of Carbon/polymer Composites For Solar Interfacial Evaporation

Nowadays,the large demand for energy and freshwater due to population explosion and overconsumption,which brings energy crisis and freshwater scarcity as two of the most severe problems in the world.It is urgent to explore renewable energy and freshwater generation methods.The seawater desalination is considered as an effective method to solve freshwater scarcity.However,the commercial desalination methods,such as reverse osmosis,multi-effect distillation and so on,which would consume traditional energy and demand complex devices.This restricts the application of commercial desalination methods in remote aeras.Solar energy,as a clean energy,which can provide convenient energy source for desalination technology.Among the existing solar desalination technologies,interfacial solar steam generation has recently attracted great attention because of high solar-to-vapor conversion efficiency.Due to these advantages,interfacial solar steam generation may expand the application of solar desalination technology in dense,independent and portable systems.As a pivotal component of interfacial solar steam generation system,solar absorbers act as photothermal converter to provide thermal energy for water evaporation.Until now,various types of solar absorbers have been developed,including metal nanoparticles,semi-conductor materials,polymer gels,and carbon-based materials.Among them,carbon materials have become a promising candidate owing to their excellent light absorption,high photothermal conversion efficiency,and chemical stability.However,traditional carbon materials are usually hydrophobic property,which is adverse to the transmission of water in carbon matrix.Meanwhile,carbon materials are often lack of flexibility,which is difficult to meet requirement of different interfacial solar steam generation systems.Moreover,most of carbon materials-based solar evaporators show low evaporation rates.So,various carbon/polymer hybrid composites have been prepared as solar absorbers for solving these problems.The research contents and results are summarized as follows:（1）In order to quickly transfer water to the surface of carbon layer and realize continuous water evaporation,a double-layer evaporator was prepared by carbon materials and hydrophilic Polyvinylidene fluoride membrane.The carbon particles were obtained through carbonization of polyester with assist of ZnO.The carbon layer exhibited excellent performance of light absorption and light-thermal conversion.Meanwhile,a hydrophilic Polyvinylidene fluoride filter membrane was chosen as supported layer,which ensured water reach at surface of carbon layer in time.Thereby,the carbon-based bilayer membrane evaporator exhibited the high evaporation rate of 1.51 kg m^-2 h^-1 and evaporation efficiency of 83.4%under one sun irradiation.（2）Based on the above work,for further enhancing the load stability of carbon materials,a high-performance flexible porous carbon/pulp fiber membrane was fabricated for interfacial solar steam generation system.Carbon particles with rich porous structures were obtained through carbonization of polyester using molten salts.Owing to the efficient energy utilization of porous carbon,the membrane exhibited excellent photothermal conversion ability.The evaporation rate and photothermal conversion efficiency under one sun irradiation were 1.80 kg m^-2h^-1 and 87.56%,respectively.Notably,the paper pulp could well combine with porous carbon,and the as-prepared porous carbon/pulp fiber membrane exhibited excellent mechanical property and flexibility.Meanwhile,the hydrophilic membrane evaporator showed remarkable cycling stability and excellent salt-resistant performance during seawater desalination.Meanwhile,the performance of outdoor seawater desalination was researched in this work.（3）The water evaporation performance is difficult to further be improved because of the existence of hydrogen bonds between water molecules.For enhancing the performance of water evaporation,a high-performance carbon hybrid hydrogel evaporator was fabricated for interfacial solar steam generation system.The as-obtained hydrogel evaporator displayed excellent light absorption ability due to the existence of carbon nanotube（CNT）.Meanwhile,Sodium lignosulfonate（SLS）enhanced the interaction between water molecules and polymer network,and significantly lowered down the water evaporation enthalpy.The evaporation rate and energy conversion efficiency under one sun irradiation were 2.09 kg m^-2h^-1 and 80.4%,respectively.Notably,the as-prepared hydrogel evaporator showed remarkable performance in solar desalination and wastewater treatment.（4）Based on the above work,to solve the problem of pollutant enrichment in the process of wastewater treatment while producing water.A multi-functional carbon/Bi₅O₇Br hybrid composite hydrogel evaporator was designed for photothermal and photocatalysis synergetic processes.This composite hydrogel exhibited excellent light-thermal conversion performance owing to the addition of carbon black and Bi₅O₇Br.The polar functional groups on the polymer network formed the hydrogen bond between water molecules to increase the content of intermediate water in hydrogel.The evaporation rate and photothermal conversion efficiency under one sun irradiation were as high as 2.61 kg m^-2 h^-1 and 92.3%,respectively.Meanwhile,Bi₅O₇Br brought the remarkable photocatalysis performance for hybrid composite hydrogel to degrade antibiotic,and the degradation rate was up to 91%.Notably,the synergetic effect between photothermal and photocatalysis process was studied in this work.