Design Of Carbon Nanotube@Dopamine/Nickel Foam Solar Evaporator And Its Photothermal Conversion Performance Study

With the rapid growth of population and the continuous acceleration of industrialization,energy scarcity,especially freshwater shortage,has become the most urgent global challenge today,and it is the common goal of mankind to find sustainable solutions.Solar energy is a green renewable energy source with broad spectrum and easy access.The technology of solar thermal conversion driven water evaporation can provide ideas for the increasingly serious energy consumption and fresh water shortage problems.Various photothermal conversion materials such as metal-based materials,semiconductor materials and carbon-based materials are widely used in solar evaporators.However,the reported evaporators are still facing many challenges in terms of preparation cost and application performance.Based on this,the present work selects nickel metal foam（NF）as the substrate and carbon nanotubes（CNTs）with full spectral range absorption capability as the photothermal conversion material,polydopamine（PDA）as the binder,and then combines the structural design of the interfacial evaporation system to prepare an efficient solar evaporator of carbon nanotubes@dopamine/nickel foam,and explores its photothermal conversion performance.The main research content as follows:（1）Preparation of nested structure evaporator and design of surface layer structure.A stable and efficient nested structure double-layer evaporator（CPNF/PU）was prepared by modifying NF with the oxidative self-polymerization reaction of PDA and depending on its viscosity to load CNTs on the surface,and then Polyurethane（PU）sponge was used as the water transport layer and polystyrene foam（PS）as the supporting and insulation layer.The evaporator has a high optical absorption capacity of91.57%in 250～2500 nm,and achieves a water evaporation rate of 1.61 kg·m^-2·h^-1 and a photothermal conversion efficiency of 90.8%at a solar radiation intensity of 1.0 k W·m^-2.Then,the wave-like physical structure of the CPNF was designed to enhance light absorption by 3D printing molds,and its water evaporation rate was increased by 5.8%compared to the one with a flat structure.Meanwhile,the evaporator can play an excellent role in seawater desalination,lake water purification,and dye wastewater treatment.What’s more,the cyclic evaporation experiments in 3.5wt%Na Cl solution show the stability of the evaporator’s use.In addition,it also shows good outdoor evaporation performance.（2）Preparation of oil sparing evaporators and related performance study.To further broaden its application scope,especially in oiled seawater.In this part,based on the photothermal layer CPNF,the two-dimensional sheet melamine sponge（MF）with better thermal insulation performance is used as the water transfer layer,and the MF is modified by using hydrophilic and oleophobic material PDDA-PFO/Si O₂,and the contact angle of the modified water transfer layer P-MF reaches 124.2°to the oil mass in the wet state,and the highly efficient oleophobic evaporator（CPNF/P-MF）is successfully prepared..The results showed that CPNF/P-MF achieved a water evaporation rate of 1.70 kg·m^-2·h^-1 and a photothermal conversion efficiency of 95.53%at a solar radiation intensity of 1.0 k W·m^-2,which was5.13%higher than that of evaporator CPNF/PU evaporator.Moreover,the evaporator CPNF/P-MF can maintain normal operation in oil-water mixed solution(V_oil:V_water=1:50,oil quality using n-hexadecane)with water evaporation rate of 1.66 kg·m^-2·h^-1.In addition,the evaporator can keep normal operation in the process of oiled seawater desalination application while the removal rate of original ions from the desalinated solution reaches 99.8%or more.This study shows that the solar-powered CPNF/P-MF has some potential for application in special environments containing oil.