Mg(NH2)2-2LiH储氢材料的研究进展

Mg(NH₂)₂-2LiH 材料是近年来发展起来的几种最具应用潜力的高容量储氢材料之一. 由于具有较合适的吸放氢热力学性能、相对较低的吸放氢操作温度、较高的可逆储氢容量和较优的吸放氢循环稳定性,Mg(NH₂)₂-2LiH 材料现已成为储氢材料研究领域的一个热点. 本文综述了Mg(NH₂)₂-2LiH 材料近年来的研究进展, 重点关注了材料的组分、晶体结构、颗(晶)粒尺寸和催化动力学改性等对材料储氢性能的影响及储氢机理,总结了Mg(NH₂)₂-2LiH 储氢材料存在的技术问题并指出了今后的研究方向.     

铁粉为原料催化改性铁氧化物的储氢性能

以Fe粉为原料, 以金属Mo, Al和Ni可溶性盐作为添加剂, 通过浸渍法制备单金属添加和双金属添加的改性铁氧化物储氢材料Fe-Mo, Fe-Al, Fe-Mo-Ni和Fe-Mo-Al, 并研究了它们的储氢性能. 结果表明样品Fe-Mo改性效果最好: 如放氢温度由改性前的500 ℃降至改性后的290 ℃左右; 300 ℃时放氢速率最高, 由改性前的低于50 μmol•min^－1• Fe-g^－1到改性后的325 μmol•min^－1•Fe-g^－1 (10次平均); 4.53 wt%的平均实验储氢量与理论值4.8 wt%较接近; 储-放氢循环稳定性随着循环次数的增加呈逐渐增加的趋势. SEM微观结构和BET比表面积分析表明添加剂的种类对样品的改性作用更重要.     

Li-Mg-N-H体系储氢材料的热力学和动力学调控

Mg（NH₂）₂-2LiH体系储氢材料具有较高的储氢容量和较适宜的热力学性能,并且其吸放氢过程完全可逆,是目前最有望实现大规模应用的固态储氢材料之一。然而,由于该体系在吸放氢过程中具有较高的动力学壁垒,导致其在200℃以上才能实现快速地吸放氢。因此,国际上对该体系储氢材料的研究主要集中在热力学和动力学的调控方面。本文从成分调变、纳米化和掺杂改性等方面,详细综述了Mg（NH₂）₂-2LiH体系储氢材料热力学和动力学调控的研究现状,并提出了其中存在的问题和相应对策,同时指出了将来的研究方向。     

硼氢化锂储氢材料研究*

车载储氢是推进氢燃料车规模化商业应用的“瓶颈”环节,开发高性能车载储氢材料/技术成为当前能源及材料领域关注的热点。近年来,随着储氢材料领域的不断拓展,以硼氢化锂（LiBH₄）为典型代表的高储量配位金属氢化物日渐成为新兴的储氢材料研究热点。本文从体系成分/反应路径调整、纳米结构调制、阴/阳离子替代及催化体系构建等方面概述了改善LiBH4综合储/放氢性能的最新研究进展,旨在明确配位硼氢化物储氢材料研究中的关键问题及可能的解决途径。     

MAlH4(M=Li,Na)储氢材料*

氢能是一种新型的清洁能源,有望替代碳经济,而氢的储存是氢能应用的关键。近年来,研究集中在具有储氢容量高和可逆性好等优点的固态储氢材料上。许多新型储氢材料不断出现,其中以MAlH₄(M=Li, Na)为代表的金属复合氢化物体系被认为是最有前景的储氢材料之一。本文综述了MAlH₄(M=Li, Na)作为可逆储氢材料的研究现状,主要从吸放氢反应、储氢性能、反应机理、理论计算和存在的问题等方面进行了讨论,并指出其相关发展趋势。     

稀土元素改性钒基固溶体储氢合金研究进展

钒基固溶体储氢合金具有体心立方(BCC)结构,储氢质量分数在3.8%以上,充放电容量为1052 mA·h/g,优于AB₂和AB₅等系列合金,并且在常温常压下表现出较高的氢溶解度和扩散系数,因此在氢储运系统以及氢能源供应等领域具有广阔的应用前景,但钒基固溶体合金存在着活化难度大、放氢条件苛刻、循环寿命短以及对氧敏感易氧化等问题。研究表明,稀土对多种固态储氢材料均有很好的改性作用,将稀土元素通过元素替代或掺杂的方式加入到钒基固溶体合金中,有助于生成高活性的稀土或稀土氧化物第二相,可明显改善材料的吸放氢热力学、循环稳定性以及抗毒化性质,同时可减少材料内的氧含量,提高材料的活化特性。电化学性能方面,稀土元素的添加能显著提升合金电极的循环稳定性、耐腐蚀能力以及高倍率放电性能。因此,稀土元素取代是实现钒基固溶体储氢材料实际应用的一项行之有效的方法。本文报道了近30年稀土改性钒基固溶体储氢合金的研究现状,重点总结了稀土元素的作用机制,并对今后重点研究方向进行了展望。     

碳纳米管-Mm(Ni-Co-Al-Mn)5复合储氢材料的电化学性能研究

本文首次研究了碳纳米管-MmNi_3.6Co_0.7Al_0.3Mn_0.4复合储氢材料的制备及其电化学性能,在250mA/g放电的条件下,其电化学储氢量达到320mAh/g,相同条件下MmNi_3.6Co_0.7Al_0.3Mn_0.4储氢量为270mAh/g.通过循环伏安法研究氢在复合电极上电化学特性表明,碳纳米管与MmNi_3.6Co_0.7Al_0.3Mn_0.4的复合促进了氢的吸附.     

Sc,Ti,V修饰B/N掺杂单缺陷石墨烯的储氢研究

3d过渡金属修饰是改善石墨烯储氢性能的最有效途径, 但仍存在金属团聚和H₂解离导致难以脱附的问题. 提出了B/N掺杂单缺陷石墨烯(BMG/NMG)的策略来避免以上两个问题. 密度泛函理论计算结果表明, N掺杂可以使Sc, Ti, V与石墨烯的结合能提高3~4倍, B掺杂可以将Sc与石墨烯的结合能提高3倍. Sc/BMG和Sc/NMG吸附的第一个H₂不会解离. Sc/BMG中Sc吸附5个H₂, 平均氢分子结合能为-0.18～-0.43 eV, 并且可以通过在同侧锚定多个Sc原子形成Sc/C₃B₂五元环增加H₂吸附位点. Sc/NMG中每个Sc吸附6个H₂, 平均氢分子结合能为-0.17～-0.29 eV, 还可以通过在异侧修饰形成Sc/N₃/Sc单元进一步提高储氢能力. 研究结果将为设计基于3d过渡金属修饰碳材料的储氢材料提供理论基础.     

五氧化二钒促进MgH2/Mg室温吸氢※

MgH₂因其储氢量高、来源广及价格低廉等优点而备受关注, 但其热力学稳定(ΔH≥76 kJ/mol-H₂)以及低温吸/放氢动力学缓慢等问题限制了它在氢能领域的广泛应用. 研究发现, 过渡金属氧化物能够显著改善MgH₂的储氢动力学性能. 系统研究了过渡金属氧化物V₂O₅对MgH₂储氢性能的改善作用. 与纯MgH₂相比, 在MgH₂中添加质量分数为5%的V₂O₅可以显著改善MgH₂的吸/脱氢动力学性能. V₂O₅掺杂MgH₂的起始脱氢温度降至175 ℃, 比同等条件处理的纯MgH₂降低了89 ℃. 值得注意的是, V₂O₅掺杂的MgH₂脱氢后, 在室温和3 MPa的氢压下, 30和180 min内吸收H₂的质量分数分别为2.1%和3.8%. 同等氢压下, 当温度提高到300 ℃时, 该样品可在1 min内吸收H₂的质量分数高达6.7%. 同时催化掺杂样品还表现出良好的循环稳定性, 20次循环后仍能维持质量分数为6.0%以上的可逆储/放氢量. 此外, V₂O₅改善MgH₂储氢性能的反应机理也通过多种手段表征得以阐明.     

添加助熔剂后朱集西煤灰熔融特性规律研究

以高灰熔点朱集西洗煤为对象,研究了助熔剂CaCO₃、Fe₂O₃、CaCO₃/Fe₂O₃复合助熔剂以及CaMg(CO₃)₂对其煤灰熔融特性的影响。结果表明,各助熔剂均可降低煤灰熔融温度,但助熔效果与助熔剂种类和添加量有关,采用CaCO₃/Fe₂O₃复合助熔剂以及CaMg(CO₃)₂在添加量较小时,助熔效果明显;利用FactSage热力学软件,分析了添加助熔剂对煤灰中矿物高温熔融行为的影响,为进一步掌握助熔剂的助熔机理提供理论帮助。     

Studies on a New Material for Hydrogen Storage and Supply by Modified Fe and Fe2O3 Powder

Modified iron oxide, a new material for hydrogen storage and supply to polymer electrolyte fuel cell （PEFC）, was prepared by impregnating Fe or Fe2O3 powder with an aqueous solution containing metal cation additives （Al, Cr, Ni, Co, Zr and Mo）. Hydrogen storage properties of the samples were investigated. The results show that both Fe and Fe2O3 powder with additive Mo presented excellent catalytic activity and cyclic stability, and their hydrogen producing temperature could be surprisingly decreased. The temperature of forming hydrogen for the Fe2O3-Mo at the rate of 250 μmol·min^-1·Fe-g^-1 could be dramatically decreased from 527 ℃ before addition of Mo to 283 ℃ after addition of Mo in the fourth cycle. The cause for it was probably related to preventing the sinter of the sample particles. In addition, hydrogen storage capacity of the Fe2O3-Mo can reach w=4.5% （72 kg H2/m^3）, close to International Energy Agency （IEA） criterion. These show the value of practical application of the Fe2O3-Mo as the promising hydrogen storage material.     

Fe_2O_3-Modified Hydrogen Storage Alloys as Electrocatalyst for Borohydride Oxidation

The effects of hot alkaline treatment and Fe₂O₃ modification of hydrogen storage alloy on the electrocatalytic activity for oxidation of borohydride have been investigated using linear sweep voltammetry. The performance of borohydride electrochemical oxidation was significantly influenced by the hot alkaline treatment and Fe₂O₃ modification of the hydrogen storage alloy. The results showed that the current density of the Fe₂O₃‐modified hot alkaline‐treated hydrogen storage alloy electrode containing 5 wt% Fe₂O₃ reached 125 mA·cm^?2 in 0.10 mol·L^?1 NaBH₄ and 2 mol·L^?1 NaOH solution at ?0.55 V vs. saturated Ag/AgCl, KCl electrode.     

通过铜(II)、铁(III)和铁(II)与2,2'-联咪唑协同作用构筑的超分子及其结构的研究

在水和乙醇溶剂中, 通过Cu(II), Fe(III)和Fe(II)与2,2-联咪唑协同作用, 构筑了四种新的超分子配合物[Cu(H₂biim)(gly)(H₂O)]Cl•H₂O (1), [Cu(H₂biim)(C₃H₂O₄)(H₂O)]•1.5H₂O (2), [Fe₂(μ-O)(H₂biim)₄(H₂O)₂](NO₃)₄•C₂H₅OH (3)和[Fe(H₂biim)₃]SO₄ (4) (H₂biim＝2,2-联咪唑; gly^－＝甘氨酸根; C₃H₂O＝丙二酸根). 并通过元素分析, 红外光谱和X射线单晶衍射对其组成、结构和谱学性质进行研究. H₂biim配体, 丙二酸根和甘氨酸根三种配体都采用了双齿螯合方式与金属离子配位. 配合物1～4中, 通过H₂biim配体的N—H键与阴离子、水分子和溶剂分子形成多种氢键, 如R(7), R(9)和R(4)等, 以及H₂biim配体之间的π-π堆积, 阳离子不对称单元构筑了多维结构的超分子配合物.     

Hydrogen production from water decomposition by redox of Fe2O3 modified with single- or double-metal additives

Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo-Cr, Mo-Ni, Mo-Zr and Mo-Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe₃O₄ (initial Fe₂O₃)+4H₂↔3Fe+4H₂O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo-Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe₂O₃-Mo-Zr, the average H₂ production temperature could be significantly decreased to 276 °C, the average H₂ formation rate could be increased to 360.9-461.1 μmol min⁻¹ Fe-g⁻¹ at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.     

High Sensitive Microsensor Based on Organic‐Inorganic Composite for Two‐Dimensional Mapping of H2O2 by SECM

The present work describes the development of a selective, sensitive and stable sensing microsensor for scanning electrochemical microscopy (SECM) to measure H₂O₂ during electrochemical reduction of oxygen. The microsensor is based on graphene and Poly(3,4‐ethylenedioxythiophene) composite as support to iron (III) hexacyanoferrate (II) (PEDOT/graphene/Fe^III₄[Fe^II(CN)₆]₃ microsensor). The electrochemical properties of the PEDOT/graphene/Fe^III₄[Fe^II(CN)₆]₃ microsensor were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The PEDOT/graphene/Fe^III₄[Fe^II(CN)₆]₃ microsensor showed an excellent electrocatalytic activity toward hydrogen peroxide (H₂O₂) reduction with a diminution of the overpotential of about 500 mV in comparison to the process at a bare gold microelectrode. The microsensor presented excellent performance for two dimensional mapping of H₂O₂ by SECM in 0.1 mol L^?1 phosphate buffer solution (pH 7.0). Under optimized conditions, a linear response range from 1 up to 1000 µmol L^?1 was obtained with a sensitivity of 0.08 nA L µmol^?1 and limit of detection of 0.5 µmol L^?1.     

磁性普鲁士蓝纳米颗粒的合成及其化学修饰电极的制作

利用FeSO₄与FeCl₃合成了超细磁性Fe₃O₄纳米颗粒, 并进一步利用该纳米颗粒与铁氰酸钾在酸性溶液(pH～2)中的化学反应成功制备了一种新型的磁性普鲁士蓝纳米颗粒; 研究了该磁性颗粒的磁学性能, 通过磁力将其修饰于固体石蜡碳糊电极表面制成了化学修饰电极, 考察了该电极对过氧化氢的电催化还原及对水合肼的电催化氧化特性. 该化学修饰电极可对过氧化氢和水合肼进行测定, 线性范围分别为过氧化氢2×10^－6～5×10^－3 mol/L, 水合肼7.2×10^－7～3.6×10^－4 mol/L. 利用磁性普鲁士蓝纳米颗粒制得的修饰电极具有催化性能高、稳定性好、表面易更新等优点.     

电沉积三维多孔Pt/SnO2薄膜及其对甲醇的电催化氧化

在高电流密度下以阴极析出的氢气泡为“模板”电沉积三维多孔Sn薄膜, 经在200 ℃ 2 h和400 ℃ 2 h热处理氧化后电沉积金属Pt, 制得三维多孔的Pt/SnO₂ (3D-Pt/SnO₂)薄膜. 通过扫描电镜(SEM)和X射线衍射(XRD)分析了薄膜的形貌和结构. 结果显示Pt主要沉积在SnO₂枝晶上, 形成Pt_shell/SnO_2core结构的枝晶. 在0.5 mol•dm^－3 H₂SO₄＋1.0 mol•dm^－3 CH₃OH溶液中的循环伏安结果表明, 3D-Pt/SnO₂薄膜电极在酸性溶液中电催化氧化甲醇的性能优于电沉积的纯铂电极, 而且具有较高的稳定性.     

Closing the Loop for Hydrogen Storage: Facile Regeneration of NaBH4 from its Hydrolytic Product

Sodium borohydride (NaBH₄) is among the most studied hydrogen storage materials because it is able to deliver high‐purity H₂ at room temperature with controllable kinetics via hydrolysis; however, its regeneration from the hydrolytic product has been challenging. Now, a facile method is reported to regenerate NaBH₄ with high yield and low costs. The hydrolytic product NaBO₂ in aqueous solution reacts with CO₂, forming Na₂B₄O₇?10 H₂O and Na₂CO₃, both of which are ball‐milled with Mg under ambient conditions to form NaBH₄ in high yield (close to 80 %). Compared with previous studies, this approach avoids expensive reducing agents such as MgH₂, bypasses the energy‐intensive dehydration procedure to remove water from Na₂B₄O₇?10 H₂O, and does not require high‐pressure H₂ gas, therefore leading to much reduced costs. This method is expected to effectively close the loop of NaBH₄ regeneration and hydrolysis, enabling a wide deployment of NaBH₄ for hydrogen storage.     

A Novel Biomimetic Hydrogen Peroxide Biosensor Based on Pt Flowers‐decorated Fe3O4/Graphene Nanocomposite

A sensitive and selective amperometric H₂O₂ biosensor was obtained by utilizing the electrodeposition of Pt flowers on iron oxide‐reduced graphene oxide (Fe₃O₄/rGO) nanocomposite modified glassy carbon electrode (GCE). The morphology of Fe₃O₄/rGO and Pt/Fe₃O₄/rGO was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The step‐wise modification and the electrochemical characteristics of the resulting biosensor were characterized by cyclic voltammetry (CV) and chronoamperometry methods. Thanks to the fast electron transfer at the Pt/Fe₃O₄/rGO electrode interface, the developed biosensor exhibits a fast and linear amperometric response upon H₂O₂. The linear range of Pt/Fe₃O₄/rGO is 0.1∼2.4 mM (R²=0.998), with a sensitivity of 6.875 μA/mM and a detection limit of 1.58 μM (S/N=3). In addition, the prepared biosensor also provides good anti‐interferent ability and long‐term stability due to the favorable biocompatibility of the electrode interface. The proposed sensor will become a reliable and effective tool for monitoring and sensing the H₂O₂ in complicate environment.