Electrochemical Knocking-Down of Zn Metal Clusters into Single Atoms.

Single Atoms Catalysts (SACs) have emerged as a class of highly promising heterogeneous catalysts, where the traditional bottom-up synthesis approaches often encounter considerable challenges in relation to aggregation issues and poor stability. Consequently, achieving densely dispersed atomic species in a reliable and efficient manner remains a key focus in the field. Herein, we report a new facile electrochemical knock-down strategy for the formation of SACs, whereby the metal Zn clusters are transformed into single atoms. While a defect-rich substrate plays a pivotal role in capturing and stabilizing isolated Zn atoms, the feasibility of this novel strategy is demonstrated through a comprehensive investigation, combining experimental and theoretical studies. Furthermore, when studied in exploring for potential applications, the material prepared shows a remarkable improvement of 58.21% for the Li+ storage and delivers a capacity over 300 Wh kg-1 after 500 cycles upon the transformation of Zn clusters into single atoms.

High Thermoelectric Performance in Phonon-Glass Electron-Crystal Like AgSbTe2.

Achieving glass-like ultra-low thermal conductivity in crystalline solids with high electrical conductivity, a crucial requirement for high-performance thermoelectrics , continues to be a formidable challenge. A careful balance between electrical and thermal transport is essential for optimizing the thermoelectric performance. Despite this inherent trade-off, the experimental realization of an ideal thermoelectric material with a phonon-glass electron-crystal (PGEC) nature has rarely been achieved. Here, PGEC-like AgSbTe2 is demonstrated by tuning the atomic disorder upon Yb doping, which results in an outstanding thermoelectric performance with figure of merit, zT ≈ 2.4 at 573 K. Yb-doping-induced enhanced atomic ordering decreases the overlap between the hole and phonon mean free paths and consequently leads to a PGEC-like transport behavior in AgSbTe2 . A twofold increase in electrical mobility is observed while keeping the position of the Fermi level (EF ) nearly unchanged and corroborates the enhanced crystalline nature of the AgSbTe2 lattice upon Yb doping for electrical transport. The cation-ordered domains, lead to the formation of nanoscale superstructures (≈2 to 4 nm) that strongly scatter heat-carrying phonons, resulting in a temperature-independent glass-like thermal conductivity. The strategy paves the way for realizing high thermoelectric performance in various disordered crystals by making them amorphous to phonons while favoring crystal-like electrical transport.

Hg Doping Induced Reduction in Structural Disorder Enhances the Thermoelectric Performance in AgSbTe2.

Defect engineering, achieved by precise tuning of the atomic disorder within crystalline solids, forms a cornerstone of structural chemistry. This nuanced approach holds the potential to significantly augment thermoelectric performance by synergistically manipulating the interplay between the charge carrier and lattice dynamics. Here, the current study presents a distinctive investigation wherein the introduction of Hg doping into AgSbTe2 serves to partially curtail structural disorder. This strategic maneuver mitigates potential fluctuations originating from pronounced charge and size disparities between Ag+ and Sb3+, positioned in octahedral sites within the rock salt structure. Hg doping significantly improves the phase stability of AgSbTe2 by restricting the congenital emergence of the Ag2Te minor secondary phase and promotes partial atomic ordering in the cation sublattice. Reduction in atomic disorder coalesced with a complementary modification of electronic structure by Hg doping results in increased carrier mobility. The formation of nanoscale superstructure with sizes (2-5 nm) of the order of phonon mean free path in AgSbTe2 is further promoted by reduced partial disorder, causes enhanced scattering of heat-carrying phonons, and results in a glass-like ultralow lattice thermal conductivity (∼0.32 W m-1 K-1 at 297 K). Cumulatively, the multifaceted influence of Hg doping, in conjunction with the consequential reduction in disorder, allows achieving a high thermoelectric figure-of-merit, zT, of ∼2.4 at ∼570 K. This result defies conventional paradigms that prioritize increased disorder for optimizing zT.

Modular Nanostructures Facilitate Low Thermal Conductivity and Ultra-High Thermoelectric Performance in n-Type SnSe.

Single crystals of SnSe have gained considerable attention in thermoelectrics due to their unprecedented thermoelectric performance. However, polycrystalline SnSe is more favorable for practical applications due to its facile chemical synthesis procedure, processability, and scalability. Though the thermoelectric figure of merit (zT) of p-type bulk SnSe polycrystals has reached >2.5, zT of n-type counterpart is still lower and lies around ≈1.5. Herein, record high zT of 2.0 in n-type polycrystalline SnSe0.92  + x mol% MoCl5 (x = 0-3) samples is reported, when measured parallel to the spark plasma sintering pressing direction due to the simultaneous optimization of n-type carrier concentration and enhanced phonon scattering by incorporating modular nano-heterostructures in SnSe matrix. Modular nanostructures of layered intergrowth [(SnSe)1.05 ]m (MoSe2 )n like compounds embedded in SnSe matrix scatters the phonons significantly leading to an ultra-low lattice thermal conductivity (κlat ) of ≈0.26 W m-1 K-1 at 798 K in SnSe0.92  + 3 mol% MoCl5 . The 2D layered modular intergrowth compound resembles the nano-heterostructure and their periodicity of 1.2-2.6 nm in the SnSe matrix matches the phonon mean free path of SnSe, thereby blocking the heat carrying phonons, which result in low κlat and ultra-high thermoelectric performance in n-type SnSe.