Synthesizing And Designing Polyaniline Thermoelectrica Composites

The global energy and environmental issues have posted serious threats to sustainabledevelopment and human health。Searching and developing new, clean, effective and reproducibleenergy has become one of the most critical issues. Thermoelectric (TE) material can realize themutual conversion between thermal energy and electric energy, which has received world wideattention due to its great potential for applications in Peltier coolers and thermoelectric powergenerators. Until now, the research of TE materials have mainly focused on inorganicsemiconductors. But inorganic thermoelectric materials are expensive, processing complex, toxicand difficicult to synthesis. Compared with inorganic thermoelectric materials, conductingpolymers thermoelectric materials (such as poly(3,4-ethylenedioxythiophene), polyaniline,Polypyrrole) have intrinsically low thermal conductivity, low toxicity, mechanical flexibility andinexpensive possibility, which have been widely considered as a potential candidate for TEmaterials. Particularly, due to the low cost, structural diversification, unique doping/dedopingprogress, low thermal conductivity and easy to synthesis. PANI is regarded as one of the mostpotential effective and suitable TE materials among conducting polymers. However, the powerfactor (S2σ) for PAN thermoelectric materials is in the range of10-6-10-10Wm-1K-2, which leadsto the serious influence on its large-scale application. Therefore, Practice application hasemployed different methods to improve the TE properties of PANI，among which one approach isto prepare organic/inorganic hybrid material so as to adjust the carrier concentration, achievinghigh ZT performance。In this paper, the following three ways are used to improve the thermoelectric properties ofpolyaniline。(1) AgNPs/PANI hybrid nanocomposites via a one-pot method using AgNO3as a precursor, DBSAas a dopant, and APS as an oxidizing agent. It is the first time that this composite was treated asthermoelectric material. AgNPs were directly reduced without any assistance reducing agent. Theas-prepared composite powder was consolidated by spark plasma sintering (SPS). Field-emissionscanning electron microscopy (FESEM) and transmittance electron microscopy (TEM) imagesshow that AgNPs with average size of20-150nm are well distributed in the PANI matrix. Thethermoelectric properties of the as-prepared AgNPs/PANI hybrid nanocomposites samples wereinvestigated and the maximum ZT of the AgNPs/PANI hybrid nanocomposites was found to be 3.8times higher than that of pure PANI.。(2) After synthesis of PANI/AgNPs nanocomposites in (1), we fabricated nanostructured PANI/AgNPs/MCNTs composites by freeze grinding method. Ag nanoparticles and carbon nano-tubesas zero and one-dimensional material reinforced thermoelectric properties of polyaniline. And thetwo phases materials can be uniformly dispersed in the PANI matrix. Finally we used XRD, FI-IR,SEM and TEM to characterize microstructures of PANI/AgNPs nanocomposite and tested theelectrical conductivity, Seebeck coefficient and thermal conductivity of the composite bulkmaterials.(3) we report a novel and green method for fabricating nanostructured rGO/PANI composites.As-synthesized rGO/PANI composite powder are prepared using cryogenic grinding (CG) withoutany dispersant. After the CG process, the grain size of PANI has been refined and rGO sheets arealso uniformly dispersed in the composites. Meanwhile, PANI well-alignedly disperses on therGO template because of the strong π-π conjugated interactions between PAN and rGO. Finall,the composites powers were consolidated via Spark Plasma Sintering (SPS). With the rGOtemplate, carrier transports are improved between the interchain and intrachain of PANI followingthe variable range hopping. An ordered chain arrangement reduce barrier of both interchainhopping and intrachain hopping and enhance the carrier mobility. Moreover, it has been foundrGO has extraordinary electrical conductivity, which becomes effective conductive medium forcarrier transmission in rGO/PANI composites. Therefore, the electrical conductivity and powerfactor of composites are found to increase with the rGO adding.