Development And Performance Study Of High Efficiency Fiber-based Photothermal Evaporation Devices

Solar-driven three-dimensional interfacial photothermal water evaporation systems are a current research hotspot to alleviate the energy crisis and freshwater shortage problem due to their lower cost,high space utilization,good evaporation performance and high photothermal conversion efficiency.Compared with the two-dimensional structure of evaporators,the design of three-dimensional interface evaporator structure can enhance light absorption,expand evaporation area,avoid the energy loss of heat transfer from the light-absorbing layer to a large amount of water bodies and optimize the energy efficiency in the solar water evaporation process.Based on the characteristics of fiber material with large specific surface area,porous structure,controllable size structure and certain mechanical strength,this thesis uses fiber material as the base material and carrier of the photothermal material,and copper sulfide and polypyrrole as the photothermal conversion materials to construct three-dimensional open hollow photothermal evaporation devices and cylindrical aerogel evaporation devices respectively.In addition,this thesis investigates the formation of Pickering foam and the catalytic performance of aramid nanofibers loaded with palladium nanoparticles as efficient and simple catalysts,which are expected to be applied in organic wastewater treatment and green synthesis.The specific research carried out is as follows:（1）A 3D opened hollow photothermal evaporator was designed using hierarchical porous Cu S-cellulose composite as a photothermal material.This unique structure not only enables the solar evaporator to have efficient water evaporation by minimizing energy loss,but also provides superior evaporation rate compared to the closed evaporator.In addition,under convection conditions,this special structure effectively promotes the escape of water vapor inside the evaporator and avoids the accumulation of water vapor,further increasing the evaporation from the inner evaporation surface,resulting in an evaporation rate of up to 11.911 kg m^-2 h^-1 at a convective flow rate of4.0 m s^-1 and 1.0 sun irradiation.The operability of the as-prepared solar evaporator under natural environmental conditions is examined by outdoor evaporation tests.The obtained solar evaporator is demonstrated to be applicable for generating clean water from model seawater and dye wastewater..（2）Cylindrical cotton fiber/aramid nanofiber/polypyrrole（CAP）aerogel evaporators were prepared by freeze-drying Pickering emulsions formulated from a hybrid system containing aramid nanofibers and pyrrole and other substances.The light absorption performance and solar water evaporation performance of the CAP aerogel evaporator were investigated.The results show that the cold evaporation surface of the evaporator can acquire a large amount of additional energy,and the evaporation rate of the evaporator at a certain height under static conditions can reach 5.435 kg m^-2 h^-1 with an energy efficiency of 173.2%,which breaks the theoretical limit of 100%.By applying convection,the steam production is further increased significantly.（3）A variety of nanocellulose was used to prepare Pickering foams.Aramid nanofibers（ANFs）were used as carriers and metallic palladium（Pd）nanoparticles were loaded on the fiber surface,and the resulting aramid-based Pd catalysts were applied to the bubble catalysis of Pickering foams.The results showed that ANFs@Pd had excellent catalytic reduction ability and good selectivity for nitroaromatic compounds,both of which could achieve 100%conversion and 99%selectivity.