Preparation And Properties Of Polypyrrole-Based Organic/Inorganic Composite Thermoelectric Materials

Nowadays,the energy crisis and environmental pollution are becoming more and more serious,and people are constantly prompted to develop and research clean and renewable energy sources.Thermoelectric materials,as an environmentally friendly material,can realize the mutual conversion between thermal and electrical energy,and are considered as a new energy supply method to realize waste heat recycling.Organic polymer thermoelectric materials have the advantages of low thermal conductivity,abundant raw materials,easy synthesis,and favorable preparation of flexible devices,but the overall thermoelectric performance is not high,which limits the practical application;traditional inorganic thermoelectric materials,their thermoelectric performance is relatively high,but the disadvantages exist at the same time,such as the non-renewable raw materials,not friendly to the environment,etc.However,organic/inorganic composite thermoelectric materials combine the advantages of each organic and inorganic,and new breakthroughs have been made in the field of thermoelectric in recent years.This thesis focuses on the synthesis and property characterization of polypyrrole（PPy）and PPy-based organic/inorganic composites with different inorganic dispersed phases,and provides experimental methods and theoretical support to solve the problem of coupling Seebeck coefficient,electrical conductivity and thermal conductivity in thermoelectric materials.This thesis mainly packages the research results in the following three parts:（1）Based on the typical P-type organic polymer PPy,this thesis optimized the synthesis process conditions of PPy according to the orthogonal design idea,and explored the effects of different oxidants,templates,polymerization time and other factors on the thermoelectric properties of PPy.The synthesis conditions of PPy were finally determined by using ferric chloride（Fe Cl₃）as oxidant,methyl orange（MO）as template agent,and polymerization for 5 h under ice bath conditions（0℃-5℃）,which provided an experimental and theoretical basis for the preparation of subsequent composites.（2）The modulation of the thermoelectric effect was achieved by preparing polypyrrole/copper oxide（PPy/x CuO）composites using CuO as the inorganic dispersed phase.The thermoelectric properties of PPy/x CuO（x=5%,10%,20%,30%）composites with different CuO weight percentages were investigated in the temperature range of 300 K-380 K.Compared with pure PPy,the electrical conductivity and Seebeck coefficient of PPy/x CuO composites could be enhanced simultaneously and thermal conductivity decreased,the conductivity of PPy/x CuO was 3946.97 S/m,Seebeck coefficient was 10.23μV/K,power factor was 0.4131μW·m^-1·K^-2,and thermal conductivity when the temperature was 300K and x=20%was 0.1255 W·m^-1·K^-1 and ZT value of 0.9874×10^-3,which was 5.2 times higher than that of pure PPy.（3）Copper-tin-sulfur（Cu₂Sn S₃）was introduced as an inorganic dispersed phase to prepare PPy/x Cu₂Sn S₃ composite thermoelectric materials,and the weight percentages of Cu₂Sn S₃ in the composites were varied to investigate the thermoelectric properties of PPy/x Cu₂Sn S₃（x=0.5%,1%,3%,5%）composites.In the temperature range of300 K-380 K,the PPy/x Cu₂Sn S₃ composite electrical conductivity,Seebeck coefficient enhanced and thermal conductivity decreased,and when the temperature was 300 K and x=1%,the ZT value of PPy/x Cu₂Sn S₃ was 1.6447×10^-3 which was8.5 times higher than that of pure PPy.