A three-in-one improvement in thermoelectric properties of polyaniline brought by nanostructures

β-Naphthalene sulfonic acid doped polyaniline nanotubes (PANI NT) was synthesized, a sample without specific nanostructure was prepared as a reference. Seebeck coefficient, electrical and thermal conductivity of both samples were studied. For a PANI NT prepared with an aniline/NSA ratio of 4:1, the Seebeck coefficient had a value of 212.4 μV/K at 300 K, which was 7 times higher than that of the reference sample. Meanwhile, electrical conductivity almost doubled, changed from 0.0045 to 0.0077 S/cm, while the thermal conductivity reduced by 27.5%, dropped from 0.29 to 0.21 W/m K. Finally, thermoelectric performance was evaluated by calculating the thermoelectric power factor and figure of merit, and there was a two orders of magnitude's increase for the tube-like PANI. A series of PANI NTs prepared under different aniline/NSA ratio were also investigated for searching an optimized performance. Tubular nanostructure was proved to be effective for enhancing the thermoelectric performance. This idea might be applicable to other organic thermoelectric materials as well.