Realizing High Thermoelectric Performance in Earth‐Abundant Bi₂S₃ Bulk Materials via Halogen Acid Modulation

Abstract

Bi2S3‐based thermoelectric materials without toxic and expensive elements have a high Seebeck coefficient and intrinsic low thermal conductivity. However, Bi2S3 suffers from low electrical conductivity, which makes it a less‐than‐perfect thermoelectric material. In this work, halogen elements F, Cl, and Br from halogen acid are successfully introduced into the Bi2S3 lattice using a hydrothermal procedure to efficiently improve the carrier concentration. Compared with the pure sample, the electron concentration of the Bi2S3 sample treated with HCl is increased by two orders of magnitude. An optimal power factor of 470 µW m−1 K−2 for the Bi2S2.96Cl0.04 sample at 673 K is obtained. Density functional theory calculations reveal that an effective delocalized electron conductive network forms after Cl doping, which raises the Fermi level into the conduction bands, thus generating more free electrons and improving the conductivity of the Bi2S3‐based materials. Ultimately, an excellent ZT of ≈0.8 is achieved at 673 K for the Bi2S2.96Cl0.04 sample, which is one of the highest values reported for a state‐of‐the‐art Bi2S3 system. The energy conversion efficiency of the module reaches 2.3% at 673 K with a temperature difference of 373 K. This study offers a new method for enhancing the thermoelectric properties of Bi2S3 by adding halogen acid in the hydrothermal process for powder synthesis.

Mediating Point Defects Endows n‐Type Bi2Te3 with High Thermoelectric Performance and Superior Mechanical Robustness for Power Generation Application

“…[3] Since the discovery of the Seebeck effect in 1821, there have been sustained efforts to increase the maximum thermoelectric conversion efficiency η max . [4][5][6]…”

Bi0.33(Bi6S9)Br compositing in Bi2S3 bulk materials forwards high thermoelectric properties

“…is the Planck constant and m* is the DOS effective mass at the Fermi level. 12 The obtained m* of Bi 2 S 3 with BSBr addition was higher than that of pure Bi 2 S 3 , and the results are shown in Table 1. sS 2 was calculated using the measured high s and S values, and the results are shown in Fig.…”

“…To date, strategies for optimizing the TE properties of Bi 2 S 3 have mainly focused on improving its s. It is reported that doping and alloying with appropriate elements are effective for improving the electrical transport properties of Bi 2 S 3 . 12,17,19 Both experiments 12,20 and first-principles calculations 21 have confirmed that Br doping is very helpful for achieving good electrical transport properties in Bi 2 S 3 . However, it is difficult to directly realize Br doping because Br 2 is a liquid and BiBr 3 is prone to hydrolysis to BiOBr during hydrothermal processing.…”

“…3 To obtain good TE properties, various strategies have been used to optimize the power factor (sS 2 ), including elemental doping, 4,5 alloying, 6,7 microstructure design, 8,9 the energy filtering effect, 10 and band engineering. 11 Efforts have also been made to reduce the lattice thermal conductivity through nanostructuring, 12 compositing, 13 and porosity design. 14 Room-temperature Bi 2 Te 3 -based TE materials have been investigated for decades and used in commercial applications owing to their good TE properties and good stability.…”

Unusual thermoelectric properties mediated by solute segregation in tellurium alloyed CoSbS

“…However, the scarcity of Te, with an abundance in the Earth's crust of around 0.001 ppm, may restrict their wide applications. Considering the signicantly high earth abundance of sulfur (S) of around 350 ppm, S-based materials, including Bi 2 S 3 , 37,38 PbS, 39,40 Cu 2 S, 41,42 and CuFeS 2 , 43,44 have received intensive interest for the replacement of their Te-based counterparts. Due to their increased ionic bonding strength, Sbased materials for thermoelectric applications are prone to exhibiting both low s and PF as a consequence of low charge carrier mobility, m H .…”