RealizingzT>2 in Environment‐Friendly Monoclinic Cu₂S—Tetragonal Cu_1.96S Nano‐Phase Junctions for Thermoelectrics

Abstract

Phase‐junction nanocomposites, made of nanograins with the same composition but different phases, offer a platform to optimize the physiochemical performance of materials. Herein, we demonstrate a straightforward strategy to synthesize Cu2−xS phase‐junction nanocomposites by retaining surface 1‐dodecanethiol (DDT) ligands, in contrast to the traditional method that strips the ligands. As a result, phase junctions between a conventional monoclinic (m) phase and an unconventional metastable tetragonal (t) phase are obtained. The significantly improved power factor is obtained due to the doping of the t‐phase. The phase‐junction interfaces reduce thermal conductivity. Finally, surface regulation of phase junctions pushes the peak zT to 2.1 at 932 K, being the highest reported for environment‐friendly metal sulfides. This work provides a paradigm to optimize thermoelectric performance by controlling phase junctions through surface‐ligand tuning.

Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution

“…Furthermore, according to the calculated energy band of CuS and Cu 2 S (Figure 2B,D), the bandgap is zero and they have good conductivity. [ 33 ] Then, X‐ray photoelectron spectroscopy (XPS) test was further conducted to clarify the electronic structure of CuS surface. Figure 2E shows the survey spectrum of CuS and Cu 2 S, indicating the existence of elements Cu, S, C, and O.…”

Recent advances in interface engineering of thermoelectric nanomaterials

“…62 Recently, a ligand retention strategy has been proposed by our group. 63,64 By compressing nanocrystals or changing the sample element ratios to form unconventional phases without eliminating long organic ligands, unprecedented enhancement of the TE properties of the materials is obtained. In this section, we will review the role of ligands in the morphology, stability and function of nanoparticles (NPs), thereby analysing the NC surface, the interaction of ligands with different chemical groups and their effect on TE properties.…”

“…4b), Li et al obtained the phase connection between the conventional monoclinic (m) phase and the unconventional metastable (t) phase as a result of retaining the ligand DDT instead of the conventional method of stripping the ligand. 64 T-phase doping significantly increases the n value and electrical transport, leading to an enhancement of the PF. At the same time, it increases phonon scattering and leads to a substantial decrease in k. Ultimately, the ZT value in the (m-Cu 2 S) 0.31 -(t-Cu 1.96 S) 0.69 sample reaches 2.11 at a temperature of 923 K. This work provides a paradigm for the enhancement of TE properties by modulating the phase-junction through surface ligand retention.…”

Balanced High Thermoelectric Performance in n-Type and p-Type CuAgSe Realized through Vacancy Manipulation

“…For instance, the zT value of Cu 2 Se, the most representative liquid-like material, can be up to 2.6 at 850 K prepared by a solid solution with In element. 23 Other liquidlike materials, such as Cu 2 S, 24 Ag 2 Te, 25 AgCrSe 2 , 26 Ag 9 GaSe 6 , 27 and Cu 5 FeS 4 , 28 have also shown excellent thermoelectric properties. Furthermore, Ag-based liquid-like materials have the potential for application in flexible thermoelectric devices due to their good ductility.…”