Preparation And Solarthermoelectric Properties Of MOFs-derived Carbon-based Composite PCMs

Phase change materials(PCMs)play an important role in the development of energy storage technology,and in promoting the development of energy conversion and storage systems and the utilization of intermittent sustainable energy.It is a key scientific problem to improve the energy efficiency of solarthermoelectric conversion system based on PCMs.It is also the key to promote the development of energy storage technology.Therefore,this paper takes PCMs as the research object and aims to strengthen the solarthermoelectric properties of composite PCMs.Starting from the structural design of metal organic frameworks(MOFs)derived carbon materials,it constructs a regular pore structure with metal particle doping and a unique MOFs-derived carbon with adjustable structure and properties.The solarthermoelectric properties,heat and mass transfer and heat storage and release characteristics of MOFs-derived carbon-based composite PCMs under multiphysical field coupling were studied.The effects of graphitization and defects on the solarthermoelectric properties of composite PCMs were revealed.Flexible MOFs-derived carbon-based solarthermoelectric composite PCMs with excellent solarthermoelectric conversion performance were developed.It provides a reliable research model and theoretical basis for the construction of flexible MOFs-derived carbon-based composite PCMs with excellent solarthermoelectric properties.Specific research contents are as follows:(1)To realize efficient solarthermoelectric conversion of composite PCMs,high graphitized magnetic carbon nanocages with Co nanoparticles doping were constructed by epitaxial growth technology and high temperature carbonization technology,and MOFs-derived carbon-based composite PCMs with high heat storage density and solarthermal performance were prepared.A new method of synergistic enhancement of solarthermal properties by magnetic nanoparticles was proposed.The coupling effect of conjugation effect and local surface plasmon resonance effect was revealed by finite element simulation,and the structureactivity relationship between the content of magnetic nanoparticles,magnetic field intensity and solarthermal properties of composite PCMs was established.The solarthermal enhancement mechanism of composite PCMs under multi-physical coupling was clarified.A solarthermoelectric conversion system based on composite PCMs was designed,and the output voltage of 290 mV and the output current of 92.6 mA were achieved.This work provides a new strategy and theoretical basis for greatly improving the solarthermoelectric properties of composite PCMs under multi-physical field coupling.(2)To further realize thermoelectric conversion based on the composite PCMs themselves,bimetallic Co/Zn-MOFs were in-situ grown on the surface of CNTs by coordination chemical reaction,and integrated CNTs@MOFs derived carbon-based solarthermoelectric composite PCMs were constructed.The influence laws of complex factors such as precursor chemical composition,pyrolysis temperature,PCMs loading capacity and type,functional group on the solarthermoelectric properties of composite PCMs were systematically explored,and the relationships between the morphology,chemical composition and the thermoelectric properties were investigated.By means of finite element simulation,the regulatory mechanism between the microscopic structure and the macroscopic thermoelectric properties was established.By optimizing the microstructure of composite materials,the synergistic intensification of solarthermal conversion and thermoelectric conversion is realized,which breaks through the record of solarthermal efficiency of composite PCMs,and the efficiency reaches 98.1%.This work provides a new strategy and theoretical basis for the design of high performance solarthermal and thermoelectric conversion and storage integrated composite PCMs.(3)Finally,to realize the overall consideration of mechanical properties and solarthermoelectric functions of composite PCMs,melamine sponge was used as the template to impregnate MOFs-derived carbon,and MOFs-derived carbon was used as the basic structural unit to construct aerogel self-supporting flexible carrier.Two kinds of efficient solarthermoelectric composite PCMs with stable structure and excellent mechanical properties were prepared by encapsulation of PCMs.The self-assembly mechanism of carbon sponges was revealed,and the influence of microstructure on mechanical properties of porous MOFs-derived carbon sponges was explored.The effects of MOFs-derived carbon on the solarthermal properties,thermoelectric properties,heat storage properties and thermal conductivity of PCMs were systematically studied.The interaction rules and coupling mechanisms of micro-nano pore space effect and carrier-PCMs interface effect on heat storage,heat transfer and solarthermoelectric properties of PCMs were clarified.This work provides a new idea for the practical application of integrated solarthermoelectric composite PCMs in wearable devices such as flexible thermal management.