Preparation And Thermoelectric Properties Of Graphene/Bi₂Te₃/PEDOT:PSS Nanocomposite Thermoelectric Materials

Thermoelectric（TE）material is an environmentally friendly material that can realize mutual conversion between thermal energy to electrical energy by the carrier’s transportation.Among all the inorganic TE materials,Bi₂Te₃ based alloys materials are the most studied TE materials with the best TE properties.Graphene has become a hot spot in the research field of composite TE materials due to its excellent electrical and mechanical properties.Conducting polymers have many advantages,such as low thermal conductivity,easy synthesis,and favorable preparation.Among them,poly（3,4 ethylene dioxythiophene）:poly（styrene sulfonic acid）（PEDOT:PSS）has become a research hot spot and has had a broad applications in the TE areas.The TE properties of inorganic/polymer composites can be enchanced when a suitable preparation method is used.However,few work on（reduced graphene oxide）rGO/Bi₂Te₃/PEDOT:PSS nanocomposite TE materials has been reported.Herein,this thesis mainly focused on the following aspects:Pure Bi₂Te₃ nanopowders and rGO/Bi₂Te₃ nanocomposite powders were prepared by a hydrothermal method.The influence of the contents of rGO on the compositions and microstructures of the composites were investigated using X-ray diffraction（XRD）,field emission scanning electron microscopy（FE-SEM）,and transmission electron microscopy（TEM）.Pure Bi₂Te₃ bulk and rGO/Bi₂Te₃ bulk nanocomposites were prepared by a hot pressed sintering method.The effects of rGO contents on the TE properties and carrier transportation of the composites were investigated.As the measurement temperature increased from 25°C to300°C,the electrical conductivities of all the rGO/Bi₂Te₃ bulk nanocomposites were decreased,and the absolute values of the Seebeck coefficients for all the samples first increased and then decreased,as a result,the power factors of the composite materials have the same trend.And a power factor of 1340μWm^-1K^-22 was obtained at 150°C for the rGO/Bi₂Te₃ nanocomposites with0.25 wt%rGO.The rGO/Bi₂Te₃ bulk composite materials containing pore-forming agent NaCl were prepared by a hot pressed sintering method after mixing rGO/Bi₂Te₃ nanopowders with NaCl powders.After removing the pore-forming agent NaCl,three dimensionally connected holes were formed in the bulk composite materials,and then rGO/Bi₂Te₃/PEDOT:PSS nanocomposite bulk materials were parepared by filling PEDOT:PSS into the as-prepared three dimensionally connected holes in the rGO/Bi₂Te₃ bulk composite skeletons.The effects of PEDOT:PSS filling procedures on the compositions and microstructures of the rGO/Bi₂Te₃/PEDOT:PSS nanocomposite bulk materials were studied.The influence of the contents of NaCl and measurement temperatures on the TE properties of bulk composite materials were investigated.A power factor of 577μWm^-1K^-2 was obtained at 100°C for the rGO/Bi₂Te₃/PEDOT:PSS nanocomposite bulk materials（pore forming agent content of 10wt%,removed）.The rGO/Bi₂Te₃ composite powders containing mercaptopropionic acid（3-MPA）were prepared by a hydrothermal process.And then the rGO/Bi₂Te₃/PEDOT:PSS composite bulk materials were prepared using the sampe procedure as the rGO/Bi₂Te₃/PEDOT:PSS composite bulk materials.The microstructures and TE properties of rGO/Bi₂Te₃/PEDOT:PSS composite bulk materials containing 3-MPA were investigated.A power factor of 851μWm^-1K^-2 was obtained at 125°C for the rGO/Bi₂Te₃/PEDOT:PSS nanocomposite bulk materials containing3-MPA（pore forming agent content of 10 wt%,removed）.