Abstract
Polypyrrole (PPy) with different morphologies (e.g., particles, nanotubes, and nanowires) were successfully prepared by adding or without adding different kinds of surfactants through a chemical oxidative polymerization method, respectively. The results show that the morphologies of PPy can be effectively controlled and have a significantly effects on their thermoelectric properties. The PPy nanowires exhibit the highest electrical conductivity and Seebeck coefficient among the various PPy morphologies, such as particles, nanotubes, and nanowires, so PPy nanowires were chosen to prepare PPy nanowire/graphene thermoelectric composites via a soft template polymerization method using cetyltrimethyl ammonium bromide as the template. Both electrical conductivity and Seebeck coefficient of the PPy nanowire/graphene composites increased as the content of graphene increases from 0 to 20 wt %, and as the measured temperature increases from 300 K to 380 K, which leds to the same trend for the power factor. A highest power factor of 1.01 μWm−1K−2 at ~380 K was obtained for the PPy nanowire/graphene composites with 20 wt % PPy nanowire, which is about 3.3 times higher than that of the pure PPy nanowire.
Highlights
Since the discovery of the Seebeck effect in 1821 by German scientist Thomas Johann Seebeck [1], most of researchers have focused on inorganic thermoelectric (TE) materials, such as Bi-Te, Pb-Te, and Si-Ge-based alloys, and this phenomenon has continued until the begining of the 21st century.More and more attention has been paid to conducing polymer TE materials and their correspondingTE nanocomposite materials [2,3,4,5].Polypyrrole (PPy), one kind of conducting polymers, has many outstanding features, such as, low density, low thermal conductivity, and easy fabrication [3,6]; PPy has a great potential for TE materials individually or as a matrix for nanocomposites
3.3 times higher than that pure at for the PPy nanowires (PPy-NWs)/graphene composites with 20 wt % of graphene
The results show that the PPy-NWs have the highest TE properties among all the morphologies of PPy
Summary
Since the discovery of the Seebeck effect in 1821 by German scientist Thomas Johann Seebeck [1], most of researchers have focused on inorganic thermoelectric (TE) materials, such as Bi-Te-, Pb-Te-, and Si-Ge-based alloys, and this phenomenon has continued until the begining of the 21st century. A PPy film was prepared by an electrochemical method, and a power factor (PF = S2 σ, where S is Seebeck coefficient and σ is electrical conductivity) of 3.9 μWm−1 K−2 (ZT value of 6.8 × 10−3 ) was achieved at 300 K [6]. A multi-walled carbon nanotube (MWCNT)/PPy composite was fabricated by an in situ polymerization method, and a power factor of 2.2 μWm−1 K−2 was achieved. It is a significant need to investigate the morphologies of PPy (e.g., PPy-PTs, PPy-NTs, and PPy-NWs) on the TE properties of themselves and their corresponding composites. To the best of our knowledge, no systematic research about the influence of morphologies of PPy (e.g., PPy-PTs, PPy-NTs and PPy-NWs) on their TE properties and PPy-NW/graphene composites has been reported. The compositions, morphologies, and TE properties of the PPy-NW/graphene composites with different contents of graphene have been investigated
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