Design Of Carbon-based Solar Evaporators And The Analysis Of Their Interfacial Evaporation Performance

In response to global freshwater and energy scarcity,people have gradually developed numerous water-cleaning technologies,however,a major drawback of most of these technologies is their high energy consumption,high costs,and substantial carbon emissions.Under the"dual carbon"strategy,cost-effective clean water production using green energy is considered one of the most promising technologies.Interface-driven solar steam generation uses sunlight energy to rapidly and efficiently convert liquid phase water into clean water via evaporation-condensation,effectively alleviating the problems of water and fossil energy shortages.Given that the ISSG technology involves the conversion of light into heat energy,heat transfer from solid phase to liquid phase,and water transportation,etc.Based on the above research mechanisms,the selection of photothermal materials and the design of evaporator structures are fundamental aspects of research and key issues for solar interface evaporation systems.At present,despite the solar evaporation efficiency continues to improve,most materials used for solar evaporators still have disadvantages such as excessive cost,poor stability,and complex preparation,which greatly limit their large-scale use in impoverished and remote areas.Furthermore,in the process of seawater desalination,the deposition of salt on the solar evaporator surface causes a significant reduction in evaporation efficiency or even results in loss of desalination capacity.Moreover,solar evaporators are unable to effectively remove organic matter from water bodies,which limiting their application.Therefore,the design and preparation of evaporators with low cost,excellent photothermal performance,outstanding salt resistance,and processability are the focus of future research in the field of solar desalination and water treatment.This thesis aims to reduce salt accumulation and improve solar evaporation efficiency,using carbon-based materials as the basis of photothermal materials,and based on the optimization theory of thermal management and exploration of water transfer mechanism,designing solar evaporators with different structures for synergy,and applying the principle of self-exhausting salt against flow diffusion as the principle of anti-salt,while combining photocatalytic technology with solar steam technology,so as to build solar evaporators for enhance the efficiency of seawater desalination and wastewater purification treatment.The main research of this thesis is as follows:（1）A 3D cone solar evaporator with strong light trapping capability was constructed using candle carbon black as the photothermal material,combined with the capillary channeling effect of adsorbed cotton water,and the effect of carbon-based photothermal material on the performance of the solar evaporator was mainly investigated.The results exhibit that under the conditions of integrating the high photothermal effect of carbon-based materials,capillary water transport action and 3D cone function,the 3D cone carbon-based evaporator achieves a water evaporation rate of 1.27 kg m^-2 h^-1 and a solar steam efficiency of 80.70%by 1k W m^-2 light.Analysis of the mechanism of the high photothermal effect of the 3D cone evaporator shows that it mainly from the following two effects,with candle carbon black as the photothermal material,the solar evaporator exhibited high efficiency photothermal conversion capability;the introduction of 3D cone structure effectively enhanced the light absorption performance and the interfacial steam generation efficiency.The results provide a reference for further design of low-cost and excellent photothermal materials and their applications in clean water production.（2）A carbon-based solar evaporator with efficient photothermal conversion was prepared by a simple coating method using filter paper as the substrate,nanodiamonds as the photothermal material,and 3D cone as the support structure.The effect of thermal management optimization on the performance of the solar evaporator was investigated.The results display that the solar steam generation efficiency reaches 82.97%under 1 k W m^-2 light,which is about 3.52 times that of pure water.The analysis of the optimized heat management strategy of the evaporator indicates it mainly comes from the following two effects.The cone insulation layer separates the contact area of the photothermal material and water greatly reduces the heat conduction loss,and the increase of the evaporation area effectively reduces the heat convection loss and heat radiation loss.In this way,the heat utilization of the solar evaporator was significantly strengthened.Analyzed from the perspective of optimal heat management,an interfacial solar thermal evaporation system with high thermal energy utilization efficiency is established.（3）A self-floating carbon-based solar evaporator was prepared using semi-coke powder as a photothermal material,polydopamine as a synergistic material,melamine sponge as a substrate,and methyltrichlorosilane as a functional hydrophobic modifier.The effect of water transport on the salt resistance of the solar evaporator was mainly investigated.The results exhibited that the solar evaporator could obtain a water evaporation rate of 1.41 kg m^-2 h^-1 and a solar steam generation efficiency of 90.56%under 1 k W m^-2 light.The SPMS showed good long-term performance by operating stably in high-concentration salt water（20 wt%Na Cl solution）experiments for 15 days.The water transport performance of the salt resistance analysis showed that the superhydrophilic nature of the evaporator and the macroporous structure promoted in-plane diffusion on the evaporation surface,which could transport salt crystals formed at the interface back to the original seawater during non-irradiated time by self-cleaning effect.Secondly,due to the hydrophobic bottom layer of evaporator can make the it float naturally on the water surface,maintaining excellent solar evaporation efficiency and long-term cycle stability.The study ensures the salt resistance of the solar evaporator through a reasonable structural design,laying the foundation for further promotion of solar desalination applications.（4）A multifunctional enhanced solar evaporator with high light trapping ability,repelling water molecules and degrading organic pollutants was prepared by modifying the surface of the carbon-based solar evaporator with dual functions of photothermal and photocatalytic by hydrophobic treatment and regulating the surface wettability of the photothermal layer.The evaporator effectively avoids the deposition of salt particles,organic matter,and other pollutants,and alleviates the problems of salt pollution and organic enrichment.The results showed that the evaporator achieved a water evaporation rate of 1.49 kg m^-2 h^-1 and93.54%solar steam efficiency under 1 k W m^-2 of light.It exhibited efficient synergistic photocatalytic degradation of organic pollutants in the treatment of complex water sources such as natural seawater,high-salinity seawater and wastewater containing organic matter.No salt accumulation was observed on its surface even after 15 d of evaporation in highly concentrated saline water,demonstrating excellent long-lasting salt resistance capability.The synergistic synergy of interfacial solar evaporation,photocatalysis,and salt tolerance provides an idea for the application of this technology in the fields of water treatment and desalination.