Reduced Hopping Barrier Potential in NiO Nanoparticle-Incorporated, Polypyrrole-Coated Graphene with Enhanced Thermoelectric Properties
Ajit Debnath, Krishna Deb, Kartick Lal Bhowmik, Bıswajıt Saha
Abstract
In view of the limiting factor in the thermoelectric conversion efficiency, an attempt has been made in this work with molecular-levelenergy barrier engineering in NiO-incorporated, polypyrrole-coated graphene (NiO@PPy/Gr). A simple, inexpensive, and ultrasonic technique has been adopted for preparation of NiO@PPy/Gr composites through an in situ oxidative polymerization process. For exploring the physical properties of the prepared NiO@PPy/Gr composites, X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images, UV–visible absorption spectra, and Raman spectra were analyzed. On studying the electrical conductivity (σ) and Seebeck coefficient (S), inspiring enhancement has been observed in thermoelectric properties of NiO@PPy/Gr as compared to those of pure polypyrrole (PPy). This enhancement is mainly attributed to the strong π–π interactions between the conjugated structure of PPy and the π-bonded surface of graphene (Gr), which leads to the formation of more ordered regions with high crystallinity in the composite. Additionally, NiO acts as a bridge between PPy and Gr in the composites, remarkably improving the charge transport and charge carrier dynamics toward enhanced thermoelectric properties. A notable 855 times enhanced power factor (PF) of 28.22 μW/mK2 was recorded as compared with that of pure PPy, with a temperature difference of only 100 °C.