Thermoelectric Properties of Polypyrrole Nanotubes
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Article www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673
Thermoelectric Properties of Polypyrrole Nanotubes Yihan Wang1 Qiang Yin*,2 Kai Du2 Site Mo3 Qinjian Yin*,1
College of Chemistry, Sichuan University, Chengdu 610065, P. R. China Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621000, P. R. China 3 College of Electrical Engineering, Sichuan University, Chengdu 610064, P. R. China 1 2
Received August 12, 2019 / Revised December 16, 2019 / Accepted December 24, 2019
Abstract: Polypyrrole (PPy) nanotubes with different diameters have been successfully prepared by different concentrations of oxidant with methyl orange (MO) as template. When the molar ratio of oxidant to pyrrole monomer was 1.5:1, PPy1.5:1 nanotubes with smooth surface and diameter of 40-60 nm were obtained. The large crystallization orientations of molecular chains in PPy nanotubes due to the template effect of MO significantly enhance π-π interactions, which improves electrical conductivity of PPy-1.5:1 nanotubes. The great degree of conjugation and the small conjugate defect of the molecular chains in PPy-1.5:1 also contribute to high mobility of carriers and high electrical conductivity. The hollow structures introduced to PPy bring about appropriate grain boundary defects and benefit seebeck coefficient of PPy nanotubes. Enhancement of electrical conductivity and seebeck coefficient of the PPy-1.5:1 nanotubes result in the maximization of power factor of 0.55 μWm-1K-2, about 22 orders of magnitude higher than PPy particles prepared under the same condition. By designing and tailoring the polymer structure, nanostructured PPy with high thermoelectric properties are highly expected. Keywords: thermoelectric, conducting polymer, polypyrrole, nanotubes, methyl orange.
1. Introduction Thermoelectric (TE) materials can realize the direct conversion between thermal energy and electric energy,1 and provide promising energy conversion system, such as power generation and refrigeration.2,3 The performance of TE materials is quantified by a dimensionless figure of merit ZT = S2σT/κ (S, σ, T, and κ are the seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively). The power factor (PF = S2σ) can also evaluate the TE properties, owing to its direct relation to the usable power attainable from the thermoelectric. So far, significant improvements in high PF have been achieved in nanostructured inorganic materials, such as SiGe, BiSbTe, and Bi2Te3.4-6 Nevertheless, the high cost and poor processability of raw materials impede their wide applications. Compared with traditional inorganic materials, conductive polymers can be key components for flexible thermoelectric devices, thanks to their abundant resources, flexibility, and low-temperature processability.2,7,8 As reported, constructing one-dimensional (1D) nanostructures in conductive polymers, including nanowires, nanotubes and nanorods, can effectively improve the carrier mobility.9-11 Acknowledgments: This work ha
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