Synthesis Of Multi-level Porous Graphene/fiber Aligned Assembly And The Study Of Photothmermal Interfacial Reactions

Solar energy,as an important renewable energy,meets modern society’s needs for green energy and sustainable development.It can be efficiently converted into other forms of energy such as electricity,fuel,and heat by using photovoltaic,photoelectric,and photothermal technologies.Photothermal conversion is the most direct solar energy conversion technology,with the highest energy conversion efficiency.As a result,photothermal conversion has been widely used in many fields in recent years,including light-driven water evaporation and catalysis.Furthermore,it has great research significance in solving the global freshwater shortage,reducing environmental pollution,leading advanced chemical catalysis,and so on.Photothermal interfacial water evaporation uses photothermal heat to accelerate the phase change of water molecules on evaporation interfaces,making it the most promising and low-cost freshwater production method that is also suitable for remote areas and emergency needs.Photothermal interfacial catalysis is a novel method for improving catalytic reaction efficiency,accelerating reactant activation,and changing the reaction path by utilizing photothermal heat to drive or accelerate catalytic reactions.The key to realizing these two high-value and novel technologies is to rationally design advanced photothermal materials with high photothermal conversion efficiencies,optimize photothermal evaporator/reactor structures to ensure rapid and directional mass transfer,and confine the photothermal heat domain to the photothermal heat domain.In this dissertation,multi-level porous graphene/fiber was used as building block,and the channel and interface structures from 1D to 3D were explored to realize the confinement of photothermal heat and the control of directional mass transfer,for efficient photothermal interfacial evaporation and photothermal interfacial catalysis,as well as to solve the problems of the narrow light absorption range,the low water evaporation efficiency of the reported materials,the unclear physical/chemical mechanism and the limited application of the photothermal interface reactions.Also,water evaporation enthalpy could be reduced by controlling the interactions between channel surfaces and water molecules.To achieve efficient interfacial evaporation,a new type of photothermal evaporator was built using the multi-level porous graphene/fiber and guided by simulations.The efficiency of photothermal conversion was increased to 80%,and the efficiency of light-to-vapor conversion was increased to exceed the theoretical limit（100%）.At the same time,a series of bottleneck problems in photothermal water evaporation were overcome,such as salt accumulation,mechanical brittleness,and low working efficiency in dark conditions.The evaporator rate only decreased 2.76%after 5 h operation in a high salinity solution of 25 wt%Na Cl,the evaporator maintained elasticity in a wide temperature range from-196°C to 700°C or even after 1000 times of reversible compressions,and the all-weather evaporation rate reached 1.63 kg·m^-2·h^-1·day^-1,ensuring the efficient and long-term evaporation.In addition,the evaporator coupled photothermal interface evaporation with photothermal interface catalysis.On the one hand,photothermal and photocatalytic materials were used to realize the absorption and utilization of the almost full-spectra light,as well as the high-speed water evaporation and water purification were completed simultaneously to remove the azeotropic volatile organic molecules in water（e.g.,Rh B molecules can be 100%transformed within 20 min）and the emerging pollutants of microplastics that are difficult to activate（e.g.,in oxygen-rich water,the degradation efficiency of fiber-shape polyethylene microplastics with an average diameter of 7μm was as high as 19%in 1 h only under light irradiation）;On the other hand,a new light-driven continuous flow catalytic reactor with the features of localized photothermal heating,photothermal induced molecular phase transition and photocatalytic molecular transformation process（e.g.,the conversion rate of P-aminophenol is as high as 97.5%）was designed,and the production strategy of high value-added products converted from pollutants under photothermal catalytic acceleration was explored.As a result,this dissertation investigates the key technologies and new coupling methods of photothermal interface water evaporation and photothermal interface catalysis based on the confinement concept of multi-level pores.Driven by the photophysical field,the heat energy transformed by photons,the water molecules and the reaction molecules are localized in the multi-level and multi-dimensional channel structures,significantly improving the efficiency of the solar-driven interfacial water evaporation and catalysis,as well as promoting the understanding of the local photothermal heating and directional mass-transfer behavior.