Transport and thermoelectric properties of polyaniline/reduced graphene oxide nanocomposites

Polyanilines (PANI)/reduced graphene oxide (RGO) nanocomposites are chemically synthesized. Their structure and morphology are characterized by scanning and transmission electron microscopies, x-ray diffraction and Raman spectroscopy. In addition, the nanocomposites' electrical, thermal and thermoelectric (TE) transport characteristics are investigated as a function of RGO content. The power factor and figure of merit (ZT) of PANI/RGO hybrids are deduced from measurements of the electrical conductivity (sigma), Seebeck coefficient (alpha) and thermal conductivity (kappa). Experimental results reveal that the properties of PANI/RGO composites are inherently dependent on the volume fraction of RGO. It is observed that electrical percolation follows a 2D conduction process which takes place for samples having 0.099 vol% RGO content. Unlike electrical conductivity, the thermal conductivity of PANI/RGO increases only slightly with the RGO fraction and is successfully fitted using a modified MGEMA model which provides an interfacial (PANI/RGO nanoplatelets) resistance (R-k) of 4.9 x 10(-10) m(2)KW(-1). This low Rk value is attributed to good interactions between the planar geometry of RGO platelets and PANI aromatic rings through pi-pi stackings as evidenced by Raman spectroscopy and x-ray studies. Compared to that of pure PANI, the TE performance of PANI/RGO composites exhibits a ZT enhancement of two orders of magnitude.