Optimization preparation of one-dimensional polypyrrole nanotubes for enhanced thermoelectric performance

Abstract

Conducting polymers with a one-dimensional (1D) morphology have a notable advantage for applications as thermoelectric (TE) materials. Compared to globular structures, such polymers can improve the electrical conductivity. The use of a proper organic compound to form a self-degraded template at the optimum concentration might be the key step in producing 1D conducting polymers with enhanced TE properties. In this work, polypyrrole (PPy) with a nanotubular morphology was synthesized in the presence of methyl orange (MO) used as a template. The effect of the MO concentration on the structural and TE properties of PPy was investigated in detail. The results obtained showed that the use of smaller amounts of MO led to the formation of a mixture of PPy nanotubes and a small amount of nanoparticles, while larger amounts of MO produced nanotubes/nanostrips. The intermediate MO values produced perfect PPy nanotubes with rectangular cavities. The optimum value of MO for maximum TE performance was determined. At room temperature (RT), the power factor was recorded as 0.75 μW/m⋅k2. This value was increased to 1 μW/m k2 by heating the sample to 383 K. The RT thermal conductivity of the produced PPy nanotubes was found to vary within the range of 0.033–0.25 W/mK depending on the amount of MO and, hence, the particle morphology. These results showed significant improvement in the figure of merit, zT, and, overall, considerable enhancement in the TE performance of PPy nanotubes, which is superior to that reported thus far.