Polymer based graphene/titanium dioxide nanocomposite (GTNC): an emerging and efficient thermoelectric material

Abstract

An ecofriendly procedure for the synthesis of graphene–titanium dioxide nanocomposites (GTNC) has been developed by dispersing nano-titanium dioxide (TiO₂) and graphene nanosheets (GNSs) in ethanol via ultrasonication followed by microwave irradiation. Such nanohybrids were characterized by X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. We have also demonstrated the synthesis of highly conductive composites like poly(3,4-ethylenedioxythiophene)polystyrene sulphonate (PEDOT:PSS)–GTNC, polyvinyl acetate (PVAc)–GTNC, PEDOT:PSS–graphene, and PVAc–graphene by ultrasonication followed by hot compaction towards their thermoelectric application. The filler (graphene, GTNC) concentration and polymer matrix were judiciously varied and optimized for the sake of high electrical conductivity and Seebeck coefficient which leads to a higher power factor (PF). The PVAc based composite with a composition of PVAc (20%) and GTNC (80%) was found to be the most promising material with an electrical conductivity of 2.6 × 10⁴ S m⁻¹ and a Seebeck coefficient of −42 μV K⁻¹ at room temperature (RT). As a result, the PF reaches 47 μW m⁻¹ K⁻² at RT which is approximately 37 times, 5 times and 3 times higher than that for the PVAc–graphene based composite, the PEDOT:PSS–GTNC based composite and the PEDOT:PSS–graphene based composite respectively. The origin of the thermoelectric performance of the GTNC composite seems to be from the synergistic effect of graphene nanosheets and TiO₂ nanoparticles. The composite shows a large power factor value without using any conducting polymer.