共查询到20条相似文献,搜索用时 15 毫秒
1.
Dr. Jiawei Zhang Dr. Daisuke Ishikawa Dr. Michael M. Koza Prof. Dr. Eiji Nishibori Dr. Lirong Song Dr. Alfred Q. R. Baron Prof. Dr. Bo B. Iversen 《Angewandte Chemie (International ed. in English)》2023,62(13):e202218458
Loosely bonded (“rattling”) atoms with s2 lone pair electrons are usually associated with strong anharmonicity and unexpectedly low thermal conductivity, yet their detailed correlation remains largely unknown. Here we resolve this correlation in thermoelectric InTe by combining chemical bonding analysis, inelastic X-ray and neutron scattering, and first principles phonon calculations. We successfully probe soft low-lying transverse phonons dominated by large In1+ z-axis motions, and their giant anharmonicity. We show that the highly anharmonic phonons arise from the dynamic lone pair expression with unstable occupied antibonding states induced by the covalency between delocalized In1+ 5s2 lone pair electrons and Te 5p states. This work pinpoints the microscopic origin of strong anharmonicity driven by rattling atoms with stereochemical lone pair activity, important for designing efficient materials for thermoelectric energy conversion. 相似文献
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Raagya Arora Umesh Waghmare C. N. R. Rao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202313852
An unusual set of anomalous functional properties of rocksalt crystals of Group IV chalcogenides were recently linked to a kind of bonding termed as metavalent bonding (MVB) which involves violation of the 8-N rule. Precise mechanisms of MVB and the relevance of lone pair of Group IV cations are still debated. With restrictions of low dimensionality on the possible atomic coordination, 2D materials provide a rich platform for exploration of MVB. Here, we present first-principles theoretical analysis of the nature of bonding in five distinct 2D lattices of Group IV chalcogenides MX (M: Sn, Pb, Ge and X: S, Se, Te), in which the natural out-of-plane expression of the lone pair versus in-plane bonding can be systematically explored. While their honeycomb lattices respecting the 8-N rule are shown to exhibit covalent bonding, their square and orthorhombic structures exhibit MVB only in-plane, with cationic lone pair activating the out-of-plane structural puckering that controls their relative stability. Anomalies in Born-effective charges, dielectric constants, Grüneisen parameters occur only in their in-plane behaviour, confirming MVB is confined strictly to 2D and originates from p-p orbital interactions. Our work opens up directions for chemical design of MVB based 2D materials and their heterostructures. 相似文献
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Dr. Eleonora Isotta Dr. Wanyue Peng Dr. Ashiwini Balodhi Prof. Dr. Alexandra Zevalkink 《Angewandte Chemie (International ed. in English)》2023,62(12):e202213649
The elastic behavior of a material can be a powerful tool to decipher thermal transport. In thermoelectrics, measuring the elastic moduli—directly tied to sound velocity—is critical to understand trends in lattice thermal conductivity, as well as study bond anharmonicity and phase transitions, given the sensitivity of elastic moduli to the chemical bonding. In this review, we introduce the basics of elasticity and explain the origin of high-temperature lattice softening from a bonding perspective. We then review elasticity data throughout classes of thermoelectrics, and explore trends in sound velocity, anharmonicity, and thermal conductivity. We reveal how experimental sound velocities can improve the accuracy of common thermal conductivity models and present a critical discussion of Grüneisen parameter estimates from elastic moduli. Readers will be equipped with tools to leverage elasticity measurements or calculations to accurately interpret thermal transport trends. 相似文献
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Chemical Modification and Energetically Favorable Atomic Disorder of a Layered Thermoelectric Material TmCuTe2 Leading to High Performance 下载免费PDF全文
Dr. Hua Lin Hong Chen Jin‐Ni Shen Prof. Ling Chen Prof. Li‐Ming Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15401-15408
Thermoelectric (TE) materials have continuously attracted interest worldwide owing to their capability of converting heat into electricity. However, discovery and design of new TE material system remains one of the greatest difficulties. A TE material, TmCuTe2, has been designed by a substructure approach and successfully synthesized. The structure mainly features CuTe4‐based layers stacking along the c axis that are separated by Tm3+ cations. Such an intrinsic Cu site vacancy structure undergoes a first‐order phase transition at around 606 K driven by the energetically favorable uniform Cu atom re‐distribution on the covalent CuTe4‐based layer substructure, as shown by crystal structure simulations and variable‐temperature XRD data. Featured with very low thermal conductivity (ca. 0.6 W m?1 K?1), large Seebeck coefficient (+185 μV K?1), and moderate electrical conductivity (220 S cm?1), TmCuTe2 has a maximum ZT of 0.81 at 745 K, which is nine times higher than the value of 0.09 for binary Cu2Te, thus making it a promising candidate for mid‐temperature TE applications. Theoretical studies uncover the electronic structure modifications from the metallic Cu2Te to the narrow gap semiconductor TmCuTe2 that lead to such a remarkable performance enhancement. 相似文献
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Concerted Rattling in CsAg5Te3 Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance 下载免费PDF全文
Dr. Hua Lin Dr. Gangjian Tan Dr. Jin‐Ni Shen Dr. Shiqiang Hao Prof. Li‐Ming Wu Dr. Nicholas Calta Dr. Christos Malliakas Si Wang Prof. Ctirad Uher Prof. Christopher Wolverton Prof. Mercouri G. Kanatzidis 《Angewandte Chemie (International ed. in English)》2016,55(38):11431-11436
Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new materials with high conversion efficiency is a great challenge because of the rare combination of interdependent electrical and thermal transport properties required to be present in a single material. The TE efficiency is defined by the figure of merit ZT=(S2σ) T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. A new p‐type thermoelectric material, CsAg5Te3, is presented that exhibits ultralow lattice thermal conductivity (ca. 0.18 Wm?1 K?1) and a high figure of merit of about 1.5 at 727 K. The lattice thermal conductivity is the lowest among state‐of‐the‐art thermoelectrics; it is attributed to a previously unrecognized phonon scattering mechanism that involves the concerted rattling of a group of Ag ions that strongly raises the Grüneisen parameters of the material. 相似文献
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Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance in AgCuTe 下载免费PDF全文
Subhajit Roychowdhury Manoj K. Jana Jaysree Pan Satya N. Guin Prof. Dirtha Sanyal Prof. Umesh V. Waghmare Prof. Kanishka Biswas 《Angewandte Chemie (International ed. in English)》2018,57(15):4043-4047
Crystalline solids with intrinsically low lattice thermal conductivity (κL) are crucial to realizing high‐performance thermoelectric (TE) materials. Herein, we show an ultralow κL of 0.35 Wm?1 K?1 in AgCuTe, which has a remarkable TE figure‐of‐merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First‐principles DFT calculation reveals several soft phonon modes in its room‐temperature hexagonal phase, which are also evident from low‐temperature heat‐capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κL in the room‐temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high‐temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor. 相似文献
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Dachang Liu Dr. Xiao Wang Xianzhao Wang Bingqian Zhang Xiuhong Sun Zhipeng Li Dr. Zhipeng Shao Prof. Sui Mao Dr. Li Wang Prof. Guanglei Cui Prof. Shuping Pang 《Angewandte Chemie (International ed. in English)》2023,62(18):e202301574
The spontaneously formed uncoordinated Pb2+ defects usually make the perovskite films demonstrate strong n-type with relatively lower carrier diffusion length and serious non-radiative recombination energy loss. In this work, we adopt different polymerization strategies to construct three-dimensional passivation frameworks in the perovskite layer. Thanks to the strong C≡N⋅⋅⋅Pb coordination bonding and the penetrating passivation structure, the defect state density is obviously reduced, accompanied by a significant increase in the carrier diffusion length. Additionally, the reduction of iodine vacancies also changed the Fermi level of the perovskite layer from strong n-type to weak n-type, which substantially promotes the energy level alignment and carrier injection efficiency. As a result, the optimized device achieved an efficiency exceeded 24 % (the certified efficiency is 24.16 %) with a high open-circuit voltage of 1.194 V, and the corresponding module achieved an efficiency of 21.55 %. 相似文献
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高效液相色谱-电感耦合等离子体质谱法分析生物样品中硒的化学形态 总被引:9,自引:0,他引:9
建立了用于生物样品中含硒化合物在线分离分析的联用方法。用反相离子对高效液相色谱(RP-IP-HPLC)分离含硒化合物,用电感耦合等离子体质谱(ICP-MS)在线分析硒含量。与标准化合物的色谱图和工作曲线对照进行定性和定量分析,实现了对硒酸钠、亚硒酸钠、硒代胱氨酸、硒代胱胺、硒代蛋氨酸、硒代尿素和三甲基硒离子等7种生物体常见的含硒小分子的分析,检出限为0.1~1.5μg/L;线性范围为1~100μg/L,应用于人血清、尿、肝组织细胞质溶胶等样品中含硒小分子的形态分析,所需进样量仅50μL,各含硒化合物加标回收率在93%~117%。本方法操作简便,灵敏度高,重现性好,适合于各种生物样品中含硒小分子的形态分析。 相似文献
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Prof. Enrique Rodríguez-Castellón Dr. Daniel Delgado Dr. Ana Dejoz Dr. Isabel Vázquez Dr. Said Agouram Dr. Juan A. Cecilia Dr. Benjamín Solsona Prof. José M. López Nieto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9371-9381
A Nb-containing siliceous porous clay heterostructure (PCH) with Nb contents from 0 to 30 wt %) was prepared from a bentonite and used as support in the preparation of supported NiO catalysts with NiO loading from 15 to 80 wt %. Supports and NiO-containing catalysts were characterised by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The characterisation studies on Nb-containing supports showed the presence of well-anchored Nb5+ species without the formation of Nb2O5 crystals. High dispersion of nickel oxide with low crystallinity was observed for the Nb-containing PCH supports. In addition, when NiO is supported on these Nb-containing porous clays, it is more effective in the ODH of ethane (ethylene selectivity of ca. 90 %) than NiO supported on the corresponding Nb-free siliceous PCH or on Nb2O5 (ethylene selectivities of ca. 30 and 60 %, respectively). Factors such as the NiO–Nb5+ interaction, the NiO particle size and the properties of surface Nin+ species were shown to determine the catalytic performance. 相似文献
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Sergio Royuela Joaquín Almarza Dr. María J. Mancheño Dr. Juan C. Pérez-Flores Dr. Enrique G. Michel Dr. María M. Ramos Dr. Félix Zamora Dr. Pilar Ocón Dr. José L. Segura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12394-12404
Lithium-sulfur batteries stands out as a promising technology for energy storage owing to a combination of favorable characteristics including a high theoretical gravimetric capacity, energy density, inexpensive character, and environmental benignity. Covalent organic frameworks (COFs) are a rapidly developing family of functional nanostructures which combine porosity and crystallinity, and which have been already used in these kinds of batteries to build sulfur electrodes, by embedding sulfur into porous COFs in order to enhance cycle lifetimes. In this contribution, this is taken one step forward and a COF endowed with vinyl groups is used, in order to graft sulfur to the COF skeleton through inverse vulcanization. The main aim of the article is to show the synergistic effect of covalent bonding and physical encapsulation of sulfur in the pores of the COF in order to alleviate the fatal redox shuttling process, to improve the cycling performance, and to provide faster ion diffusion pathways. In addition, it is shown how the material with covalently-bound S provides better electrochemical performance under demanding and/or changeable charge conditions than a parent analogue material with sulfur physically confined, but without covalent linkage. 相似文献
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A Molecular Approach to Manganese Nitride Acting as a High Performance Electrocatalyst in the Oxygen Evolution Reaction 下载免费PDF全文
Carsten Walter Dr. Prashanth W. Menezes Steven Orthmann Jona Schuch Paula Connor Dr. Bernhard Kaiser Prof. Dr. Martin Lerch Prof. Dr. Matthias Driess 《Angewandte Chemie (International ed. in English)》2018,57(3):698-702
The scalable synthesis of phase‐pure crystalline manganese nitride (Mn3N2) from a molecular precursor is reported. It acts as a superiorly active and durable electrocatalyst in the oxygen evolution reaction (OER) from water under alkaline conditions. While electrophoretically deposited Mn3N2 on fluorine tin oxide (FTO) requires an overpotential of 390 mV, the latter is substantially decreased to merely 270 mV on nickel foam (NF) at a current density of 10 mA cm?2 with a durability of weeks. The high performance of this material is due to the rapid transformation of manganese sites at the surface of Mn3N2 into an amorphous active MnOx overlayer under operation conditions intimately connected with metallic Mn3N2, which increases the charge transfer from the active catalyst surface to the electrode substrates and thus outperforms the electrocatalytic activity in comparison to solely MnOx‐based OER catalysts. 相似文献
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《Analytical letters》2012,45(16):2324-2333
A new, sensitive, and simple HPLC method was described for the determination of 1-aminocyclopropane-1-carboxylic acid (ACC) in apple and peach extracts. The method was based on the derivatization of ACC with fluorescamine in borate buffer systems of pH 8.0 to yield a highly fluorescent product. The experimental parameters affecting the derivatization reaction efficiency were optimized by fluorimetric analysis. Under optimum derivatization conditions, the derivative product of ACC in apple and peach extracts without extra purification was successfully chromatographed on a C-18 column by HPLC coupled to fluorescence detection. The derivative product of ACC with fluorescamine could be well separated from other concomitant substances or their derivatives that might interfere with the determination of ACC. The linearity of ACC was measured in the range of 23.82–238.82 µg · L?1 with a good correlation coefficient of 0.9997. Based on signal-to-noise ratio of 3, a low detection limit of 5.0 µg · L?1 could be reached. The proposed method was applied successfully to the determination of ACC in the crude apple and peach extracts without extra purification with low RSDs of 0.19–1.9% and good recoveries of 90.89–104.4%. The sensitive HPLC quantitative method is of great significance for the investigations of ACC metabolism in plants. 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
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Li Rong WEN Gui Long ZHAO Ming LI Wen Ying QI Xiu Li ZHANG Hua Zheng YANG 《中国化学快报》2005,16(9):1161-1164
It has been known that pyrazole ring has two main tautomeric isomers1-3as showed in Scheme1.The proton could migrate at the two nitrogen atoms of the pyrazole ring.Taylor E.C.and Purdum W.R.4first reported the synthesis of2as an isomer of2a.And so far,only a few literatures5-6have reported that this pyrazole derivative was in form2a,rather than2,therefore both acylation or alkylation reaction occurred at N-1of2a.But the regiochemistry of the N-substituted product of pyrazole has not been u… 相似文献