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SnSe has attracted much attention due to the excellent thermoelectric (TE) properties of both p‐ and n‐type single crystals. However, the TE performance of polycrystalline SnSe is still low, especially in n‐type materials, because SnSe is an intrinsic p‐type semiconductor. In this work, a three‐step doping process is employed on polycrystalline SnSe to make it n‐type and enhance its TE properties. It is found that the Sn0.97Re0.03Se0.93Cl0.02 sample achieves a peak ZT value of ≈1.5 at 798 K, which is the highest ZT reported, to date, in n‐type polycrystalline SnSe. This is attributed to the synergistic effects of a series of point defects: VSe.., ClSe.,VSn,,,ReSn×, Re 0. In those defects, the VSe.. compensates for the intrinsic Sn vacancies in SnSe, the ClSe. acts as a donor, the VSn,, acts as an acceptor, all of which contribute to optimizing the carrier concentration. Rhenium (Re) doping surprisingly plays dual‐roles, in that it both significantly enhances the electrical transport properties and largely reduces the thermal conductivity by introducing the point defects, ReSn×, Re 0. The method paves the way for obtaining high‐performance TE properties in SnSe crystals using multipoint‐defect synergy via a step‐by‐step multielement doping methodology. [ABSTRACT FROM AUTHOR]

Lithium–air batteries (LABs) have attracted intense interest due to their ultrahigh energy density. However, the performance of LABs has to depend on modified electrolytes, gas selective film and Li anode protection. In this study, firstly it is reported that Mo‐O octahedron induced subcrystalline scheelite CoMoO4 catalyst achieves a high performance LABs performance based only on the high catalytic activity in air. The subcrystalline CoMoO4 catalyst obtains a specific capacity of 12 000 mAh g−1, and ultralong cycle stability over 270 cycles at 1000 mA g−1 in ambient air. This study demonstrates an ultrastable crystal structure and surface conditions of the CoMoO4 catalyst toward a corrosive environment and complex air‐involved reactions. A theoretical calculation further reveals that the polyhedral framework in the scheelite CoMoO4 can provide a highly stable catalytic surface for the OER/ORR reactions, furthermore, its repulsive nature toward H2O and CO2 can efficiently avoid side reactions and slow the corrosion of the Li anode in air. Moreover, the induced octahedron enhances the adsorption energies to O2 and LiO2, and accelerates the catalytic reactions in air. The present study provides a conceptual breakthrough to find highly active cathode catalysts for LABs. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) generally exists in electrochemistry‐enabled applications that are coupled with cathodic reactions like hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. The OER heavily impacts the overall energy efficiency of these devices because the sluggish OER kinetics result in a huge overpotential, thus, a large amount of efficient catalysts are needed. The benchmark iridium and ruthenium (Ir/Ru)‐based materials (mostly used in acid media) are, however, significantly limited by their scarcity. Non‐precious metal‐based catalysts (NPMCs) have emerged as the most promising alternatives; however, they tend to degrade quickly under the harsh operating conditions of typical OER devices. Another challenge is the unsatisfying performance of OER catalysts when integrated in real‐world devices. Herein, the OER active sites for three mainstream types of NPMCs including non‐precious transition metal oxides/(oxy)hydroxides, metal‐free carbon materials, and hybrid non‐precious metal and carbon composites are reviewed. In addition, possible degradation mechanisms for active sites and mitigation strategies are discussed in detail. This review also provides insights into the gaps between R&D of NPMCs for the OER and their applications in practical devices. [ABSTRACT FROM AUTHOR]

A facile method to prepare flexible n‐type Ag2Se/Se/polypyrrole (PPy) composite films is developed. First, Ag2Se nanostructures (NSs) are wet chemically synthesized; PPy is then in situ polymerized at the surface of the Ag2Se NSs; and finally, the Ag2Se/Se/PPy composite film on a porous nylon membrane is fabricated by a vacuum‐assisted filtration process followed by hot pressing. An optimal composite film shows an exceptionally high power factor of ≈2240 µW m−1 K−2 at 300 K, mainly because of the synergistic effect between well‐developed crystalline Ag2Se grains and a small amount of Se and PPy. The film also possesses outstanding flexibility (only about 6.5% decrease in electrical conductivity after 1000 times bending along a rod with a radius of 4 mm). Moreover, a flexible thermoelectric generator composed of six legs of the film outputs a voltage of 21.2 mV and a maximum power of 4.04 µW (corresponding power density of 37.6 W m−2) at a temperature difference of 34.1 K, verifying exceptionally high thermoelectric properties. This work shows the promise of the as‐prepared composite film for practical applications in wearable devices and will surely promote the research and development of flexible TE generators. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Keywords: bismuth sulfide; halogen acid; hydrochloric acid; hydrothermal doping EN bismuth sulfide halogen acid hydrochloric acid hydrothermal doping 1 1 1 09/13/21 20210909 NES 210909 B Halogen Acid Modulation b In article number 2102838, Zhen-Hua Ge, Xiaohua Yu, Jing Feng, Jiaqing He, and co-workers present a new strategy that can significantly improve the electrical transport properties, as well as reduce the lattice thermal conductivity at 673 K in Bi SB 2 sb S SB 3 sb materials. Realizing High Thermoelectric Performance in Earth-Abundant Bi2S3 Bulk Materials via Halogen Acid Modulation (Adv. Funct. Bismuth sulfide, halogen acid, hydrochloric acid, hydrothermal doping. [Extracted from the article]

Halogen Acid Modulation In article number 2102838, Zhen‐Hua Ge, Xiaohua Yu, Jing Feng, Jiaqing He, and co‐workers present a new strategy that can significantly improve the electrical transport properties, as well as reduce the lattice thermal conductivity at 673 K in Bi2S3 materials. Due to the optimized electrical conductivity by hydrochloric acid doping during the hydrothermal procedure, nanostructured Bi2S3 with a high ZT value of 0.8 is obtained. [ABSTRACT FROM AUTHOR]