Strategy for enhanced thermoelectric performance of Bi2S3 nanorods by Bi nanoinclusions

TL;DR

This study reports a novel synthesis of Bi2S3-Bi nanocomposites with significantly improved thermoelectric properties at room temperature, achieved through a one-step polyol method that reduces electrical resistivity and enhances power factor.

Contribution

First demonstration of enhanced thermoelectric performance in Bi2S3-Bi nanocomposites synthesized via a simple one-step polyol process at various reaction conditions.

Findings

Electrical resistivity decreases with higher reaction temperature and time.

Power factor at 300 K is three orders of magnitude greater than pure Bi2S3.

The nanocomposites show potential for high thermoelectric efficiency near room temperature.

Abstract

This is the first report on the enhanced thermoelectric (TE) properties of novel Bi2S3-Bi nanocomposites synthesized using a one-step polyol method at different reaction temperatures (TRe) and time. They are well-characterized as nanorod-composites, coexistent with orthorhombic Bi2S3 and rhombohedral Bi phases together in which the latter coats the former forming Bi2S3-Bi core-shell type structures along with independent Bi nanoparticles (NPs). There is a very significant observation of systematic reduction in electri-cal resistivity \r{ho} with reaction temperature and time duration increase, revealing a promising approach for reduction of \r{ho} in this highly resistive Bi2S3 and hence resolving the earlier obstacles for its thermoelectric application potentials for the past few decades. Most astonishingly, TE power factor at 300 K of highest Bi content nanocomposite pellet, made at 27 oC using ~900 MPa pressure, is 3 orders of magnitude greater than that of hot-pressed Bi2S3, or even 23% better than that of spark plasma-sintered core-shell Bi2S3@Bi sample reported earlier (Tarachand et al. Nano Res. 2016, 9, 3291; Ge et al. ACS Appl. Mater. Interfaces 2017, 9, 4828). Considering the probable greatly reduced thermal conductivity due to their complex nanostructures, the significantly improved TE performance potential near 300 K is highly anticipated for these toxic- and rare earth element-free TE nanocomposites, making the present synthesis method as a pioneering approach for developing enhanced thermoelectric properties of Bi2S3-based materials without using extra sintering steps.