Preparation Of Polyaniline-based Thermoelectric Composites And Thermoelectric Performance Research

Thermoeletric material is a kind of functional materials which can realize the conversion of thermal energy and electricity interactively through carrier transporting in solid.They have great potential applications in electricity harvesting from temperature difference,or in the recycling of automobile exhaust and waste heat of industry.Polymer has drawn more attention in thermoelectrics because of its intrinsically low thermal conductivity,good solution processability,high abundance and low price.Polyaniline(PANI)is one of the most promising polymer which has the great potential application in industrial production.However,the performance of PANI is far away from actually using,so incorporating low-dimensional nano-materials into PANI matrix to optimize thermoelectric properties has become the research hotspot.In this paper,carbon nanotubes(CNTs)and reduced graphene oxide(RGO)were chosen as the filling template,while poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)was used as dispersing stabilizer to realize the homogeneously dispersion of fillers.Then aniline monomer was polymerized on the surface of the template to form the ordered chain structure.Finally,CNTs/PEDOT:PSS/PANI,RGO/PEDOT:PSS/PANI and CNTs/RGO/PEDOT:PSS/PANI.XRD and FE-SEM were used to characterize the structures of composites.Electrical conductivity,Seebeck coefficient and thermal conductivity were measured to study the thermoelectric performance.We study the influence of the ratio of fillers to PEDOT:PSS,filler content,and the ratio of CNTs to RGO on the performance of composites.It is concluded as below:(1)For CNTs/PEDOT:PSS/PANI composite,stabilizer PEDOT:PSS was used to disperse CNTs.With the ratio of PEDOT:PSS to CNTs increased,thermoelectric performance of composite retively improved.When the ratio of CNTs to PEDOT:PSS was 1:4,ZT of composites reached 1.21×10-6.While the CNTs content increased,the contact distance decreased which facilitate the carrier transporting and increase the conductivity of composites.Meanwhile,owing to the energy percolation effect and the phono scattering effect at the phase interface,electricalconductivity and seebeck coefficient improved synergeticly,while the thermal conductivity decreased,so ZT enhanced.When the content of CNTs reached 50%,ZT of composite is2.09×10-5 which is about 31 times over the pure PANI.(2)We prepared RGO/PEDOT:PSS/PANI composite by in situ polymerization.With the RGO increased,bigger interface areas were introduced into composite,so the energy filtration effect of composite enforced which lead to the enhancement of Seebeck coefficient.Meanwhile,with the RGO increased,electrical conductivity increased and finally thermoelectric properties improved.When the RGO content reached to 50%,ZT of this material reached to 7.25×10-6which was about 10.5 times larger than that of pure PANI.(3)We prepared CNTs/RGO/PEDOT:PSS/PANI composite by in situ polymerization.One-dimensional CNTs and two-dimensional RGO have the synergistic effect due to the strong interaction between them.When the ratio of CNTs to RGO is 2:1,synergistic effect is more obvious.With the fillers increased,electrical conductivity,Seebeck coefficient and ZT enhanced respectively.At the 50% filler content,ZT reached to 2.38×10-5,which was 1.2 times over than CNTs/PEDOT:PSS/PANI with 50% CNTs filling,and 3.3 times larger than RGO/PEDOT:PSS/PANI with 50% RGO filling and 36 times than that of pure PANI.