Investigating thermoelectric properties of doped polyaniline nanowires

Polyaniline (PANI) nanostructures doped with different acids have been prepared through a soft template method. The structures, morphologies and thermoelectric (TE) properties of the as-prepared PANI nanostructures have been carefully investigated. Our results showed that doping level, types of doping acids, and morphologies of as-prepared nanostructures did have strong effect on TE properties. For example, we found that higher doping level in HCl-doped PANI nanowires did not give better thermoelectric performance although it is true in some curtain doping range. AcOH-doped samples became worse than HCl-doped ones due to the poor doping ability of AcOH. As to p-toluenesulfonic acid (p-TSA) doped nanowires, ZT value is 2.75 × 10^-5 at 300 K, which is 4 times higher than that of HCl-doped one because doped bulky anions make PANI chains more order. As to the morphology effect, two p-TSA doped samples (nanowires and nanorods) at the same doping level were prepared and the nanowires showed the better Seebeck coefficient and lower thermal conductivity. Comparing with nanorods, Seebeck coefficient of nanowires increased 164% while thermal conductivity reduced by 25% for nanowires. The ZT value for nanowires is 5 times higher than that of nanorods.