共查询到20条相似文献,搜索用时 15 毫秒
1.
光催化技术可以直接将太阳能转化为化学能,制造化学燃料或环境友好的产品。然而,常用的光催化剂大多为具有宽能隙的半导体材料,所需光源大多在紫外区,对太阳光的利用率不高;并且电子-空穴复合率高,导致光催化反应效率低。币金属纳米团簇具有超小尺寸(<2 nm)和分立能级,能够实现电子和空穴的分离,电子结构可调,可以通过调节其电子结构进而提高其光催化性能。同时,精确的原子级组成和结构使其成为一种在原子水平上探索光催化机制的理想模型。本文报道了基于币金属纳米团簇的光催化反应的现状,包括水分解产氢、有机污染物降解和光催化氧化胺等。通过探讨调节币金属纳米团簇的光催化性能的策略,对币金属纳米团簇光催化剂的发展前景予以展望。 相似文献
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W. Bronger 《无机化学与普通化学杂志》1996,622(1):9-16
The Atomic Volume of Hydrogen in Metal Hydrides in Comparison with Corresponding Fluorides and Chlorides The atomic volume of hydrogen in metal hydrides is calculated by using the atomic volumes of the metal cations as given by Biltz. The exceptional polarizability of hydrogen ligands is the reason for its adaptability when forming different bond structures in metal hydrides. The atomic volume of hydrogen decreases from 13.7 cm3mol?1 in salt-like caesium hydride to 3.9 cm3mol?1 in metallic palladium hydride. This variation is significantly higher for metal hydrides than for metal chlorides, although the volume of a hydrogen ion is comparable to that of a fluoride ion, that shows an almost constant value in its compounds. For structurally related hydrides an examination of the atomic volume of hydrogen allows the re-examination of a given composition and therefore the disclosure of a wrong atomic arrangement. 相似文献
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P. Modrak 《Progress in Surface Science》1995,48(1-4):233-244
The surface segregation of one component in binary transition metal alloys and the surface segregation of one hydrogen isotope in transition metal hydrides containing a mixture of hydrogen isotopes are discussed in the scope of the same thermodynamic model. The binary alloys are assumed to form a disordered substitutional alloy and the random distribution of hydrogen isotopes is assumed in the case of transition metal hydrides. 相似文献
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Summary The technique developed earlier for the generation of the so-called first-order polarized basis sets for accurate non-relativistic calculations of molecular electric properties is used to obtain similar basis sets suitable for calculations in the Douglas-Kroll no-pair approximation. The corresponding (relativistic) basis sets are devised for atoms of the Groups Ib and IIb of the periodic table and tested in calculations of atomic polarizabilities and dipole moments of the coinage metal hydrides. Excellent performance of these basis sets has been found in the case of molecular calculations. 相似文献
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《Journal of Energy Chemistry》2020,(3)
Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also,for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alkaline earth aluminum hydrides and correlates structure properties with physical and chemical properties of the hydride compounds. The crystal structures of the alkali metal aluminum hydrides change significantly during the stepwise dehydrogenation. The general pathway follows a transformation of structures built of isolated [AlH4]~- tetrahedra to structures built of isolated [Al H6]~(3-) octahedra.The crystal structure relations in the group of alkaline earth metal aluminum hydrides are much more complicated than those of the alkali metal aluminum hydrides. The structures of the alkaline earth metal aluminum hydrides consist of isolated tetrahedra but the intermediate structures exhibit chains of cornershared octahedra. The coordination numbers within the alkali metal group increase with cation sizes which goes along with an increase of the decomposition temperatures of the primary hydrides. Alkaline earth metal hydrides have higher coordination numbers but decompose at slightly lower temperatures than their alkali metal counterparts. The decomposition pathways of alkaline metal aluminum hydrides have not been studied in all cases and require future research. 相似文献
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液相化学氢化物以化学键的形式储存氢能,被认为是一类很有前景的化学储氢材料。液相化学氢化物的大规模应用很大程度上依赖于高效催化系统的开发。含金金属纳米颗粒在用于液相化学氢化物催化制氢中表现出优异的催化性能。本文综述了金纳米颗粒和含金异金属纳米颗粒用于液相氢化物催化制氢的最新研究进展。 相似文献
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Hui Wu 《Chemphyschem》2008,9(15):2157-2162
Metal hydrides are an important family of materials that can potentially be used for safe, efficient and reversible on‐board hydrogen storage. Light‐weight metal hydrides in particular have attracted intense interest due to their high hydrogen density. However, most of these hydrides have rather slow absorption kinetics, relatively high thermal stability, and/or problems with the reversibility of hydrogen absorption/desorption cycling. This paper discusses a number of different approaches for the improvement of the hydrogen storage properties of these materials, with emphasis on recent research on tuning the ionic mobility in mixed hydrides. This concept opens a promising pathway to accelerate hydrogenation kinetics, reduce the activation energy for hydrogen release, and minimize deleterious possible by‐products often associated with complex hydride systems. 相似文献
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Complex metal hydrides are perhaps the most promising hydrogen storage materials for a gradual transformation to a hydrogen-based economy. We have used a computational approach to aid the ongoing experimental effort to understand the reversible hydrogen storage in Ti-doped NaAlH(4) and propose a plausible first step in the rehydrogenation mechanism. The study provides insight into the catalytic role played by the Ti atoms on an Al surface in the chemisorption of molecular hydrogen and identifies the local arrangement of the Ti atoms responsible for the process. Our results can potentially lead to ways of making other similar metal hydrides reversible. 相似文献
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The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments. Catalytic activity was found to be influenced by four distinct physico-thermodynamic properties of the transition-metal compound: a high number of structural defects, a low stability of the compound, which however has to be high enough to avoid complete reduction of the transition metal under operating conditions, a high valence state of the transition-metal ion within the compound, and a high affinity of the transition-metal ion to hydrogen. On the basis of these results, further optimization of the selection of catalysts for improving sorption properties of magnesium-based hydrides is possible. In addition, utilization of transition-metal compounds as catalysts for other hydrogen storage materials is considered. 相似文献
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This paper describes a reaction mechanism that explains the dehydrogenation reactions of alkali and alkaline-earth metal hydrides. These light metal hydrides, e.g., lithium-based compounds such as LiH, LiAlH4, and LiNH2, are the focus of intense research recently as the most promising candidate materials for on-board hydrogen storage applications. Although several interesting and promising reactions and materials have been reported, most of these reported reactions and materials have been discovered by empirical means because of a general lack of understanding of any underlying principles. This paper describes an understanding of the dehydrogenation reactions on the basis of the interaction between negatively charged hydrogen (H-, electron donor) and positively charged hydrogen (Hdelta+, electron acceptor) and experimental evidence that captures and explains many observations that have been reported to date. This reaction mechanism can be used as a guidance for screening new material systems for hydrogen storage. 相似文献
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In this tutorial review recent mechanistic studies on transition metal-catalyzed hydrogen transfer reactions are discussed. A common feature of these reactions is that they involve metal hydrides, which may be monohydrides or dihydrides. An important question is whether the substrate coordinates to the metal (inner-sphere hydrogen transfer) or if there is a direct concerted transfer of hydrogen from the metal to substrate (outer-sphere hydrogen transfer). Both experimental and theoretical studies are reviewed. 相似文献
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B. P. Tarasov M. V. Lototskii V. A. Yartys’ 《Russian Journal of General Chemistry》2007,77(4):694-711
Merits and demerits of existing methods of hydrogen storage are discussed. Special attention is given a metal hydride technology based on the ability of metals, intermetallic compounds, and alloys for reversible reaction with hydrogen. It is noted that the basic advantages of metal hydrides are a high volumetric hydrogen content, operational safety, technological flexibility, and low power inputs on hydrogen absorption and desorption. 相似文献
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Belkova NV Gutsul EI Filippov OA Levina VA Valyaev DA Epstein LM Lledos A Shubina ES 《Journal of the American Chemical Society》2006,128(11):3486-3487
The interaction of CpM(CO)3H (M = Mo, W) hydrides as proton donors with different bases (B = pyridine, (n-Oc)3PO, ((CH3)2N)3PO, H3BNEt3) was studied by variable temperature IR spectroscopy and theoretically by DFT/B3LYP calculations. The data obtained show for the first time the formation of intermolecular hydrogen bonds between the neutral transition metal hydrides and bases in solutions of low polarity. These M-H...B hydrogen bonds are shown to precede the hydrides' deprotonation. 相似文献
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Churchard AJ Banach E Borgschulte A Caputo R Chen JC Clary D Fijalkowski KJ Geerlings H Genova RV Grochala W Jaroń T Juanes-Marcos JC Kasemo B Kroes GJ Ljubić I Naujoks N Nørskov JK Olsen RA Pendolino F Remhof A Románszki L Tekin A Vegge T Zäch M Züttel A 《Physical chemistry chemical physics : PCCP》2011,13(38):16955-16972
The widespread adoption of hydrogen as an energy carrier could bring significant benefits, but only if a number of currently intractable problems can be overcome. Not the least of these is the problem of storage, particularly when aimed at use onboard light-vehicles. The aim of this overview is to look in depth at a number of areas linked by the recently concluded HYDROGEN research network, representing an intentionally multi-faceted selection with the goal of advancing the field on a number of fronts simultaneously. For the general reader we provide a concise outline of the main approaches to storing hydrogen before moving on to detailed reviews of recent research in the solid chemical storage of hydrogen, and so provide an entry point for the interested reader on these diverse topics. The subjects covered include: the mechanisms of Ti catalysis in alanates; the kinetics of the borohydrides and the resulting limitations; novel transition metal catalysts for use with complex hydrides; less common borohydrides; protic-hydridic stores; metal ammines and novel approaches to nano-confined metal hydrides. 相似文献
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Hydrogen‐rich materials are potential high‐temperature superconductors at pressures lower than metal hydrogen, mainly because hydrogen atoms can provide strong electron–phonon coupling and high phonon frequencies in hydrogen‐rich materials. This review provides a systematic overview of the crystal type, stability, pressure‐induced transition, metallization and superconductivity of binary light‐metal hydrides under high pressure. 相似文献
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Electron-richPolynuclearTransitionMetalClusters:Ⅱ.SyntheticandStructuralStudiesofSomePolynuclearCoinageMetalClusterCompoundsH... 相似文献
20.
Bingqing Lin Xi Wu Prof. Dr. Lin Xie Yongqiang Kang Prof. Dr. Hongda Du Prof. Dr. Feiyu Kang Prof. Dr. Jia Li Prof. Dr. Lin Gan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20528-20532
Resolving interstitial hydrogen atoms at the surfaces and interfaces is crucial for understanding the mechanical and physicochemical properties of metal hydrides. Although palladium (Pd) hydrides hold important applications in hydrogen storage and electrocatalysis, the atomic position of interstitial hydrogen at Pd hydride near surfaces still remains undetermined. We report the first direct imaging of subsurface hydrogen atoms absorbed in Pd nanoparticles by using differentiated and integrated differential phase contrast within an aberration-corrected scanning transmission electron microscope. In contrast to the well-established octahedral interstitial sites for hydrogen in the bulk, subsurface hydrogen atoms are directly identified to occupy the tetrahedral interstices. DFT calculations show that the amount and the occupation type of subsurface hydrogen atoms play an indispensable role in fine-tuning the electronic structure and associated chemical reactivity of the Pd surface. 相似文献