Construction Of Flexible Conjugated Polymer/Carbon Nanotubes Composite Thermoelectric Materials And Their Application For CO₂ Emission Control

Thermoelectric materials have developed rapidly and have great application potential in waste heat recovery in various fields.They can improve energy efficiency and reduce emissions of gas pollutants from the source.Based on the research of conjugated polymer molecular structure design and internal construction of composite thermoelectric materials,three new polymers were mixed with single-walled carbon nanotubes（SWCNTs）by physical blending and chemical doping technology to prepare flexible thin films.The thermoelectric properties,microstructure characterization,chemical and structural information characterization of the composite film were analyzed.Meanwhile,the effects of the composite film on devices,waste heat recovery and pollutant emission control were estimated.The details are as follows:（1）Starting from the common thermoelectric material polythiophene,the structure,morphology and physical properties of Guerbet alkyl side chain polythiophene and single-walled carbon nanotubes composites were investigated,and the relationship between structure morphology and thermoelectric properties of composites was discussed in detail.The polymer containing alkyl side chains was added to make the structure of the single-walled carbon nanotube network more uniform,dispersed and closely bonded with the single-walled carbon nanotube.By changing the number of alkyl side chains,the conjugation effect of the main chain was effectively changed,resulting in a more regular arrangement and a tighter and more orderly binding of the single-walled carbon nanotubes to the polymer.The good interaction between the two can promote the transfer of carriers at the interface and trigger the energy filtration effect,so as to improve the thermoelectric performance of the composite membrane.Due to the coupling effect,the increase of carrier mobility will reduce the concentration of carrier at the same time,so the increase of Seebeck coefficient decreases the conductivity,and then increases the thermal stability of the conductivity of the composite film.The power factor is up to 134μW/m K².（2）Based on Poly（3,4-vinyl dioxthiophene）,the structure,morphology and physical properties of sulfonated agglutinate（3,4-vinyl dioxythiophene）and single-walled carbon nanotubes composites were investigated,and the relationship between the structure morphology and the thermoelectric properties of the composites was discussed in detail.The results of FESEM showed that the polymer poly（3,4-ethylenedioxthiophene）containing sulfuric acid groups and the network structure of single-walled carbon nanotubes showed layer structure,which did not change the original network morphology,but played a role in separating the two network structures.Different from the action mode of alkyl side chain,the addition of sulfonic acid group makes the composite structure of poly（3,4-vinyl dioxythiophene）main chain and inorganic nanomaterials adjust to layer structure.The power factor is up to 134μW/m K².This study revealed the mechanism of different functional groups adjusting the main chain morphology of different conjugated polymerization,and provided a new idea and way for the subsequent research and development of new thermoelectric materials.（3）The structure,morphology and physical properties of polar side chain polythiophene and single-walled carbon nanotubes composites were investigated by synthesizing the effects of alkyl side chains and oxygen atoms on the construction of composite films,and the relationship between structure morphology and thermoelectric properties of composites was discussed in detail.The study showed that the attraction between polar side chain polythiophene was stronger than that between alkyl side chain polythiophene.The polymer formed wraps on the surface or in the crevices of single-walled carbon nanotubes,making the interstitials in the bundle structure tighter.When polar side chain polythiophene was added,the conductivity of the composite films was significantly improved.According to the research results,the highest conductivity reached 1891 S/cm.In the tight microstructure of the composite film,the polar side-chain polymer played a role in adjusting the structure of the single-wall carbon nanotube network,and became a new bridge for the carrier transport between the single-wall carbon nanotubes.Similar to the composite films of sulfonyl agglomerated（3,4-vinyl dioxthiophene）/single-walled carbon nanotubes,Seebeck coefficient decreased,with the increase of temperature,Seebeck coefficient also showed an increasing trend,similarly,the power factor also showed a similar rule,up to 540μW/m K²,high temperature field,it has a huge waste heat utilization potential.（4）With polar side chain polythiophene composite film and copper foil as raw materials,the preparation method of thermoelectric devices and device performance testing and analysis,as well as based on device performance evaluation for carbon dioxide emission reduction prediction.When the temperature difference reaches 50 K,the open-circuit voltage is 12.95m V,the maximum output power is 936 n W,and the power density is 4.88 m W/m².At this time,the temperature at the hot end is 98℃,and the temperature at the cold end is 39.4℃.The tendency of the thermoelectric device to enhance its performance with increasing temperature indicates that it has a wide range of applications.Taking a 300 MW coal-fired unit in Sanhe Electric Power Plant as an example,according to the actual design,the total heat exchange area of the waste heat recovery system of the unit is 28460 m²,and according to the power density of thermoelectric devices is 4.88 m W/m²,it is estimated that the annual power generation can be 760 kw·h,and the waste heat utilization can save 0.565 t of standard coal.Although the emission reduction effect of gas pollutants is relatively weak,it is the first attempt to calculate the actual effect of the device.The structure and manufacturing process of the device need to be further optimized to better adapt to the special working environment.Therefore,for conjugated polymers with thiophene groups as the main chains,Guerbet alkyl and oxygen atomic groups（C-O-C and-SO₃H）can be added to the side chains by means of molecular design,so as to change the composite structure between the polymer and single-walled carbon nanotubes.The phonon scattering effect between the polymer and carbon nanotubes can effectively reduce the thermal conductivity.The addition of new groups can also change the energy level band gap of organic matter,and the energy filtration effect of heterojunction can be used to effectively regulate the carrier concentration and mobility,so as to obtain the ideal conductivity and Seebeck coefficient,and achieve the purpose of improving the thermoelectric performance.