Preparation of polypyrrole/graphene nanosheets composites with enhanced thermoelectric properties

Polypyrrole/graphene nanosheets (PPy/GNs) composites with enhanced thermoelectric properties have been successfully synthesized by a simple in situ chemical polymerization method with the weight ratio of Py to GNs ranging from 1 : 0.1 to 1 : 0.4. FTIR, Raman spectra, SEM and XRD analyses show that strong pi-pi interactions exist between PPy and GNs, and during polymerization the PPy grew along the surface of the GNs to form a more ordered molecular structure with increased crystallinity. The thermoelectric properties of PPy and PPy/GNs composites were investigated after being cold pressed at room temperature. As the GNs content increases, the Seebeck coefficient can be effectively improved and a remarkably enhanced electrical conductivity has been obtained, while the thermal conductivity of the composites shows no significant change even with high GNs content. As a result, the thermoelectric figure of merit ZT increases with increasing GNs content and the maximum ZT value of 2.80 x 10(-3) is obtained for the composite with the highest GNs content, which is about 210 times higher than that obtained from pure PPy. The results of thermogravimetric analysis indicate that the PPy/GNs composites exhibit better thermal stability than pure PPy.