PEMFC备用氢能发电站的储氢问题探讨

在介绍目前国内外各种成熟的工业储氢方法,并指出储氢技术研究热点和发展方向的基础上,针对人防工程备用氢能发电站的技术要求,对各种适用的储氢方式进行了比较,探讨了人防工程备用氢能发电站的氢气储存方法,以及氢气安全储存、运输与监控、反应热处理等问题。     

氢敏材料与器件的研究进展

氢气的检测具有重要的学术意义和广阔的应用前景.氢敏传感器发展的关键在于高品质氢敏材料的研制.本文根据氢敏材料工作原理的不同,分别介绍了电化学型、半导体型、热导型和光学型四类氢敏传感器及相应氢敏材料的国内外研究最新进展,着重描述了各类氢敏材料的作用机制和改性途径,并展望了氢敏材料及氢敏传感器的发展方向.     

Metallic Hydrogen

One of the great challenges in condensed matter physics has been to produce metallic hydrogen (MH) in the laboratory. There are two approaches: solid molecular hydrogen can be compressed to high density at extreme pressures of order 5–6 megabars. The transition to MH should take place at low temperatures and is expected to occur as a structural first-order phase transition with dissociation of molecules into atoms, rather than the closing of a gap. A second approach is to produce dense molecular hydrogen at pressures of order 1–2 megabars and heat the sample. With increasing temperature, it was predicted that molecular hydrogen first melts and then dissociates to atomic metallic liquid hydrogen as a first-order phase transition. We have observed this liquid–liquid phase transition to metallic hydrogen, also called the plasma phase transition. In low-temperature studies, we have pressurized HD to over 3 megabars and observed two new phases. Molecular hydrogen has been pressurized to 4.2 megabars. A new phase transition has been observed at 3.55 megabars, but it is not yet metallic.     

Hydrogen energy

The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.     

Kinetics-Driven Dual Hydrogen Spillover Effects for Ultrasensitive Hydrogen Sensing

Palladium (Pd)-modified metal oxide semiconductors (MOSs) gas sensors often exhibit unexpected hydrogen (H₂) sensing activity through a spillover effect. However, sluggish kinetics over a limited Pd-MOS surface seriously restrict the sensing process. Here, a hollow Pd-NiO/SnO₂ buffered nanocavity is engineered to kinetically drive the H₂ spillover over dual yolk-shell surface for the ultrasensitive H₂ sensing. This unique nanocavity is found and can induce more H₂ absorption and markedly improve kinetical H₂ ab/desorption rates. Meanwhile, the limited buffer-room allows the H₂ molecules to adequately spillover in the inside-layer surface and thus realize dual H₂ spillover effect. Ex situ XPS, in situ Raman, and density functional theory (DFT) analysis further confirm that the Pd species can effectively combine H₂ to form Pd-H bonds and then dissociate the hydrogen species to NiO/SnO₂ surface. The final Pd-NiO/SnO₂ sensors exhibit an ultrasensitive response (0.1–1000 ppm H₂) and low actual detection limit (100 ppb) at the operating temperature of 230 °C, which surpass that of most reported H₂ sensors.     

Application of the Hydrogen Diffusion Model to the Hydrogen Permeation

The model of hydrogen diffusion formerly de-veloped [1] has been applied successfully to thehydrogen permeation experiment results of threekinds of materials,α—Fe,Fe—Ti alloy and Fe—Ti—Calloy by the mathematical fitting method.From thefitting results it was shown that the model can re-fiect well the diffusion of hydrogen in the materialswith trapping.The obtained trapping parameters(αand β)can be used to explain well the diffusion ofhydrogen in the samples with trapping.     

Hydrogen in semiconductors

Hydrogen in crystalline semiconductors has become a recent curiosity because of its high diffusivity and strong chemical activity in such materials. In contrast to the proton motion in ionic materials which gives rise to an enhanced conductivity, hydrogen in electronic materials interact with structural disorders and chemical impurities to control the electronic flow. Deep gap states in crystalline semiconductors due to various disorders such as surface/interface, grain boundaries, dislocations, irradiation and implantation damage etc. have been removed due to hydrogen bondings. Hydrogen incorporation is done by plasma and direct ion beam hydrogenation methods, implantation technique and by a novel technique of damage free introduction. The most studied materials are silicon and gallium arsenide.I - V,C - V, DLTS and IR studies have been carried out on hydrogenated semiconductors to characterize the electronic flow, gap states and the nature of chemical bonds. Improvement in ideality factors of diodes, reduction in free carrier concentration, removal or reduction of deep states and appearance of new bondings such as Si-H, P-H, B-H etc. have been observed from various techniques. The present paper reviews the various features of hydrogenation studies in crystalline silicon and gallium arsenide and highlights our results of hydrogenation studies on Pd/semiconductor devices.     

Hydrogen multicentre bonds

The concept of a chemical bond stands out as a major development in the process of understanding how atoms are held together in molecules and solids. Lewis' classical picture of chemical bonds as shared-electron pairs evolved to the quantum-mechanical valence-bond and molecular-orbital theories, and the classification of molecules and solids in terms of their bonding type: covalent, ionic, van der Waals and metallic. Along with the more complex hydrogen bonds and three-centre bonds, they form a paradigm within which the structure of almost all molecules and solids can be understood. Here, we present evidence for hydrogen multicentre bonds-a generalization of three-centre bonds-in which a hydrogen atom equally bonds to four or more other atoms. When substituting for oxygen in metal oxides, hydrogen bonds equally to all the surrounding metal atoms, becoming fourfold coordinated in ZnO, and sixfold coordinated in MgO. These multicentre bonds are remarkably strong despite their large hydrogen-metal distances. The calculated local vibration mode frequency in MgO agrees with infrared spectroscopy measurements. Multicoordinated hydrogen also explains the dependence of electrical conductivity on oxygen partial pressure, resolving a long-standing controversy on the role of point defects in unintentional n-type conductivity of ZnO (refs 8-10).     

Hydrogen in metals

The effects of hydrogen on various metals and the use of metal hydrides for hydrogen storage are discussed. The mechanisms of, and differences between, hydrogen embrittlement and hydrogen attack of ferritic steels are compared, common sources of hydrogen in metals processing and treatment identified, and mechanisms for hydrogen entry into a ferritic surface are discussed. The differences between hydrogen attack of ferritic steels and copper alloys are contrasted, and an unusual case study of hydrogen embrittlement of an alloy steel is presented.     

Hydrogen bonded perrhenate-azoimidazoles

Reaction in aqueous medium of KReO₄ in methanolic solution of RaaiCH₂Ph (1-benzyl-2-(arylazo)imidazole) (1) in the presence of perchloric acid has isolated brown products of {[1-benzyl-2-(arylazo)imidazolium][ReO₄⁻]H₂O}_n, 2. The structural confirmation has been carried out by the single crystal X-ray diffraction study of {[1-benzyl-2-(phenylazo)imidazolium][ReO₄⁻]H₂O}, 2a. The molecules are polymerized via hydrogen bonding and form cross-linked network.     

氢敏变色材料

在众多的氢气泄漏检测方法中,光学色敏示氢检漏法显示出其本质安全的特点.简要介绍了主要类型的氢气检测方法及示氢敏感元件的工作原理,并对可逆氢敏变色材料的发展、应用作了展望.     

氢燃料电池用氢中杂质分析方法综述

介绍了质子交换膜燃料电池用氢气中14种气态杂质的可能来源以及对氢燃料电池系统的影响。对国际标准中的建议方法以及国内外相关文献中的离线检测方法进行总结,分析各种检测方法的优缺点。根据国内相关标准物质的数据,分析了标准研制的难点,并提出了可行的研制方案,报道了研究进展。概述加氢站氢气在线分析的相关文献,总结了在线分析可能的发展趋势。最后,根据氢燃料电池的现状与应用范围,展望了氢燃料电池的未来发展方向。     

Mg-Ni储氢合金箔的制备及储氢性能研究

根据机械合金化和界面固相扩散反应的基本原理,开创性地提出了机械碾压法加化学镀配料加氢化燃烧合成的三步合成工艺,制备出高容量的Mg-Ni储氢合金.研究表明,气相燃烧过程中的温度、压力及保温时间对燃烧产物的组成有较大的影响,通过对反应过程的分析得出了合成Mg-Ni合金箔的反应机理.热分析测试表明所得Mg-Ni合金箔在220℃放氢,放氢量为2.6wt%.     

Chiral Plasmonic Hydrogen Sensors

In this article, a chiral plasmonic hydrogen‐sensing platform using palladium‐based nanohelices is demonstrated. Such 3D chiral nanostructures fabricated by nanoglancing angle deposition exhibit strong circular dichroism both experimentally and theoretically. The chiroptical properties of the palladium nanohelices are altered upon hydrogen uptake and sensitively depend on the hydrogen concentration. Such properties are well suited for remote and spark‐free hydrogen sensing in the flammable range. Hysteresis is reduced, when an increasing amount of gold is utilized in the palladium‐gold hybrid helices. As a result, the linearity of the circular dichroism in response to hydrogen is significantly improved. The chiral plasmonic sensor scheme is of potential interest for hydrogen‐sensing applications, where good linearity and high sensitivity are required.