Ti-Zr-V-Cr-Ni固溶体贮氢合金电极的制备和电化学性能

根据工作环境的要求,镍-金属氢化物电池不仅要满足电源在室温时的工作需要,还应满足在不同工作条件下的需求,如高温、低温等,这就需要电极在较宽的温度范围内具有优异的性能。改性的AB5合金电极在343K时的放电容量能达到265mAh·g-1左右(截止电压为0.5V,相对于Hg/HgO参比电极)[     

Ti0.17Zr0.08V0.34Nb0.01Cr0.1Ni0.3氢化物电极合金微观结构及电化学性能研究

采用XRD、FESEM-EDS、ICP及EIS等方法研究了Ti_0.17Zr_0.08V_0.34Nb_0.01Cr_0.1Ni_0.3氢化物电极合金微观结构和电化学性能。X射线衍射分析表明：该合金由体心立方结构(bcc)的V基固溶体主相和少量六方结构的C14型Laves相组成；FESEM及EDS分析表明：V基固溶体主相形成树枝晶，C14型Laves相呈网格状围绕着树枝晶的晶界，元素在两相中的分布呈现镜像关系。电化学性能测试结果表明：该合金的氢化物电极在303~343 K较宽的温度区间内，表现出较高的电化学容量，在303 K和343 K时，电化学容量分别为337.0 mAh·g^-1和327.9 mAh·g^-1。在303 K循环100周后，容量为282.7 mAh·g^-1。ICP分析结果表明，氢化物电极在充放电循环过程中，V及Zr元素向KOH电解质中的溶出较为严重。EIS研究表明，金属氢化物电极表面电化学反应的电荷转移电阻(R_T)随循环次数的增加而增加，相应的交换电流密度则随循环次数的增加而降低。氢化物电极循环过程中RT的增大以及V和Zr元素的溶解，可能是导致电极容量衰减的主要原因。     

Effect of LiH on electrochemical hydrogen storage properties of Ti55V10Ni35 quasicrystal

The electrochemical hydrogen storage properties and mechanisms of the Ti₅₅V₁₀Ni₃₅ quasicrystal + xLiH(x = 3, 6 and 9 wt.%) system are investigated and discussed in this paper. A composite material in the Ti₅₅V₁₀Ni₃₅ quasicrystal and system has been synthesized moderately by means of mechanical milling under an argon atmosphere, which can avoid reaction of releasing of hydrogen during the process of milling. The results indicate that the addition of LiH significantly improves the electrochemical characteristics of composite material. The maximum discharge capacity increases from 220.1 mAh/g to 292.3 mAh/g on Ti₅₅V₁₀Ni₃₅ + 6 wt.% LiH, and the cycling stability is also enhanced too. In addition, the high rate dischargeability (HRD) is ameliorated remarkably, and the value of HRD value at 240 mA/g rises by 78.1%–87.8% for Ti₅₅V₁₀Ni₃₅ + 6 wt.% LiH alloy electrodes. The improvement of characteristics of the electrochemical hydrogen storage characteristics may be attributed to LiH, which has excellent electrochemical activity.     

稀土元素取代对Ti0.26Zr0.07V0.24Mn0.1Ni0.33贮氢合金结构和电化学性能的影响

研究了5种稀土元素部分取代V对Ti_0.26Zr_0.07V_0..24Mn_0.1Ni_0.33合金的微观结构和电化学性能的影响。结果表明,Ti_0.26Zr_0.07V_0.24Mn_0.1Ni_0.33和Ti_0.26Zr_0.07V_0.24-xMn_0.1Ni_0.33RE_x（x=0.005;RE=La,Ce,Nd,Ho,Y）均由体心立方结构的钒基固溶体相和六方结构的C14Laves相组成。在合金中加入稀土元素,会使合金中两相的晶胞体积同时增大。稀土元素部分取代V均改善了合金电极的活化性能。La和Nd元素取代后,合金电极的最大放电容量明显增加,而Ce的取代提高了合金电极的循环稳定性。Ce,Nd,Ho,Y均改善了合金电极的倍率放电性能。合金电极在高温状态下表现出了良好的放电性能,其中Nd在333K时放电容量可达550.4mAh·g^-1。稀土元素对荷电保持率的影响各异。     

稀土元素取代对Ti_(0.26)Zr_(0.07)V_(0.24)Mn_(0.1)Ni_(0.33)贮氢合金结构和电化学性能的影响

研究了5种稀土元素部分取代V对Ti0.26Zr0.07V0..24Mn0.1Ni0.33合金的微观结构和电化学性能的影响。结果表明,Ti0.26Zr0.07V0.24Mn0.1Ni0.33和Ti0.26Zr0.07V0.24-xMn0.1Ni0.33REx(x=0.005;RE=La,Ce,Nd,Ho,Y)均由体心立方结构的钒基固溶体相和六方结构的C14 Laves相组成。在合金中加入稀土元素,会使合金中两相的晶胞体积同时增大。稀土元素部分取代V均改善了合金电极的活化性能。La和Nd元素取代后,合金电极的最大放电容量明显增加,而Ce的取代提高了合金电极的循环稳定性。Ce,Nd,Ho,Y均改善了合金电极的倍率放电性能。合金电极在高温状态下表现出了良好的放电性能,其中Nd在333 K时放电容量可达550.4 mAh·g-1。稀土元素对荷电保持率的影响各异。     

硼的添加对Ti0.26Zr0.07V0.24Mn0.1Ni0.33贮氢合金结构和电化学性能的影响

Ti_0.26Zr_0.07V_0.24Mn_0.1Ni_0.33Bx(x=0~0.10)系列合金均有V基固溶体相和C14型Laves相两相组成。添加B可提高Ti_0.26Zr_0.07V_0.24 Mn_0.1Ni_0.33合金的放电容量, Ti_0.26Zr_0.07V_0.24Mn_0.1Ni_0.33B0.1合金电极在60 mA·g^-1电流放电时的放电容量达到476.7 mAh·g^-1.B的添加不同程度地降低了合金的高倍率放电性能, 使合金电极表面上电化学反应的电荷转移电阻(R_ct)显着增加, 交换电流密度(I₀)显着降低。添加B可显着改善Ti_0.26Zr_0.07V_0.24Mn_0.1Ni_0.33合金电极的高温放电性能, Ti_0.26Zr_0.07V_0.24Mn_0.1Ni_0.33B_0.025合金电极在343 K高温下其放电容量达到525.6 mAh·g^-1.     

硼的添加对Ti0.26Zr0.07V0.24Mn0.1Ni0.33贮氢合金结构和电化学性能的影响

Ti0.26Zr0.07V0.24Mn0.1Ni0.33Bx(x=0~0.10)系列合金均有V基固溶体相和C14型Laves相两相组成。添加B可提高Ti0.26Zr0.07V0.24Mn0.1Ni0.33合金的放电容量,Ti0.26Zr0.07V0.24Mn0.1Ni0.33B0.1合金电极在60 mA·g-1电流放电时的放电容量达到476.7 mAh·g-1。B的添加不同程度地降低了合金的高倍率放电性能,使合金电极表面上电化学反应的电荷转移电阻(R ct)显著增加,交换电流密度(I0)显著降低。添加B可显著改善Ti0.26Zr0.07V0.24Mn0.1Ni0.33合金电极的高温放电性能,Ti0.26Zr0.07V0.24Mn0.1Ni0.33B0.025合金电极在343 K高温下其放电容量达到525.6 mAh·g-1。     

Effect of Ti substitution on hydrogen storage properties of Zr1−xTixCo (x = 0, 0.1, 0.2, 0.3) alloys

Zr_1−xTi_xCo (x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-temperature (PCT) measurements were carried out using Sievert's type volumetric apparatus for ZrCo (at 473 K, 573 K and 673 K) and Zr_1−xTi_xCo alloys (at 673 K), respectively. Products after dehydrogenation were characterized by X-ray diffraction (XRD). In addition, the kinetics of Zr_1−xTi_xCo hydride was investigated at 473 K and 673 K, respectively, under hydrogen pressure of 5 MPa. Results showed that Ti substitution for Zr did not change the crystal structure of ZrCo phase. With the increase of temperature from 473 K to 673 K, the extent of disproportionation for ZrCo alloy increased. With Ti content increasing at 673 K, the desorption equilibrium pressure of Zr_1−xTi_xCo-H₂ systems elevated and the disproportionation reaction of Zr_1−xTi_xCo alloys was inhibited effectively. Ti substitution decreased the kinetics rate and the effective hydrogen storage capacity of Zr_1−xTi_xCo alloys slightly. Generally speaking, it was found that Zr_0.8Ti_0.2Co alloy had better anti-disproportionation property with less decrease of effective hydrogen storage capacity which was beneficial to tritium application in the International Thermonuclear Experimental Reactor (ITER).     

Electrochemical characterization of negative electrodes consisting of surface-modified Zr0.9Ti0.1(Ni1.1Co0.1Mn0.5V0.2Cr0.1)x Laves-phase alloys

Laves-phase hydrogen storage alloy has a high potential for use as negative electrode material as alternative for the misch-metal-based material. In order to improve the energy density and the rate capability of negative electrode, chemical and mechanical modification of Lavesphase alloy with different stoichiometric ratios was carried out. Discharge capacity and high-rate dischargeabilty was evaluated by electrochemical methods and the characterization of Laves-phase alloy was made by X-ray diffraction, SEM observation and PCT measurement. The best result in discharge capacity could be obtained for stoichiometric Laves-phase alloy with a composition of Zr_0.9Ti_0.1Ni_1.1Co_0.1Mn_0.5V_0.2Cr_0.1 by boiling in 10 M KOH solution. On the other hand, the high-rate dischargeability was increased remarkably by introducing mechanical grinding before alkali treatment. The cause for improved performance was discussed on the basis of thermodynamic stability of metal hydride and changes in crystal structure and surface morphology influencing on diffusion coefficient and diffusion path length of hydrogen.     

Effects of Ti and Zr Substituted on the Electrochemical Characteristics of MgNi-Based Alloy Electrodes

Mg-based hydrogen storage alloys MgNi, Mg0.9Ti0.1Ni, and Mg0.9Ti0.06Zr0.04Ni were successfully prepared by means of mechanical alloying （MA）. The structure and the electrochemical characteristics of these Mg-based materials were studied. The X-ray diffraction （XRD） result shows that the main phases of the alloys exhibit amorphous structure. The scanning electron microscopy （SEM） photograph shows that the particle size of Ti and Zr substituted alloys was about 2-4 μm in diameter. The cycle lives of the alloys were prolonged by adding Ti and Zr. After 50 charge-discharge cycles, the discharge capacity of Mg0.9Ti0.06Zr0.04Ni was 91.74% higher than that of MgNi alloy and 37.96% higher than that of Mg0.9Ti0.1Ni alloy. The main reason for the electrode capacity decay is the formation of Mg（OH）2 （product of Mg corrosion） at the surface of alloy. The potentiodynamic polarization result indicates that Ti and Zr doping improves the anticorrosion in an alkaline solution. The electrochemical impedance spectroscopy （EIS） results suggest that proper amount of Ti and Zr doping improves the electrochemical catalytic activity significantly.     

Fe部分替代Cu对低钴AB_5型贮氢合金相结构和电化学性能的影响

为了获得既具有较高电化学容量又具有良好循环稳定性的低钴AB5型贮氢合金,研究了Fe部分替代Cu对低钴AB5型贮氢合金相结构和电化学性能的影响.采用真空感应熔炼方法,制备了一系列含Cu和Fe的低钴AB5型贮氢合金LaNi3.55Mn0.35Co0.20Al0.20Cu0.85-xFex(x=0.10,0.20,0.25,0.40,0.60).粉末X射线衍射(XRD)分析表明,合金含有单一CaCu5型六方结构的LaNi5相,Fe部分替代Cu并没有改变合金的本体相结构,但随着Fe含量的增大,晶格参数a,c和晶胞体积V增大.电化学性能测试表明,随着x增加,合金的放电容量和高倍率放电能力降低,但是循环稳定性得到了显著提高.当x从0.10增加到0.60时,合金的200周循环稳定性(S200)从77.6%提高到89.9%.Fe替代Cu有利于提高合金的循环稳定性,这主要是随着Fe替代量增大,晶胞体积增大,晶格体积膨胀率明显减小,合金的抗粉化能力增强.     

一种具有低SO2氧化活性并满足欧V排放标准的柴油车氧化型催化剂

制备了具有高性能的稀土储氧材料Ce_0.75Zr_0.25O₂-Al₂O₃,Ti_0.9Zr_0.1O₂复合材料和Cr改性的β分子筛(Cr-β分子筛),并以此制备了单Pt型柴油车尾气净化氧化型催化剂.低温N₂吸附-脱附、储氧量测试结果表明,Ce_0.75Zr_0.25O₂-Al₂O₃样品具有较大的比表面积和优异的储氧性能,Ti_0.9Zr_0.1O₂复合材料也具有优越的织构性能.催化剂对HC和CO具有较高的催化活性,可使SOF在140℃开始转化,且具有较低的SO₂氧化活性.在YC4F国Ⅳ柴油机的测试结果表明,经该催化剂处理后的尾气排放能够满足欧Ⅴ排放标准对HC和CO排放要求.     

稀土元素对Ti0.26Zr0.07V0.24Mn0.1Ni0.33贮氢合金微观结构和电化学性能的影响

本文研究了稀土元素对Ti0.26Zr0.07V0.24Mn0.1Ni0.33合金的微观结构和电化学性能的影响。结果表明,Ti0.26Zr0.07V0.24-xMn0.10Ni0.33REx(RE=Ce,Nd,Gd;x=0.01)合金均有V基固溶体相和C14型Laves相两相组成。合金中两相的晶格参数随加入稀土元素的不同而发生变化。稀土元素部分取代可改善合金电极的活化性能。然而,对合金电极的其他性能影响因元素种类不同而各异。Ce取代增大了合金电极的最大放电容量,Nd元素可以有效改善合金的高倍率放电性能。工作温度对合金电极的放电容量影响较大,Nd和Gd在333 K最大放电容量可达426和465 mAh.g-1。过高的温度使其循环容量衰减加剧。     

Ti-V-Nb-Cr-Ni电极合金的微观结构及某些动力学性能研究

本文采用XRD，FESEM-EDS及电化学阻抗谱(EIS)等方法对V基固溶体Ti_0.25V_0.34Nb_0.01Cr_0.10Ni_0.30电极合金的微观结构及某些动力学性能，如交换电流密度(i₀)、氢的扩散系数(D)等进行了研究。XRD和FESEM-EDS分析测试结果表明：Ti_0.25V_0.34Nb_0.01Cr_0.10Ni_0.30电极合金由BCC结构的V基固溶体主相和少量的TiNi基第二相组成，其中，V基固溶体主相为树枝晶形状，TiNi基第二相呈网格状围绕着树枝晶。EIS及其等效电路分析结果表明，电极表面电化学反应的电荷转移电阻(R_T)随着温度的升高而降低，而交换电流密度和氢在合金本体中的扩散系数随着温度的升高而升高。在343 K时的交换电流密度分别为323 K和303 K的3.6倍和13.6倍，氢的扩散系数略有升高。电化学反应的表观活化能(Δ_rH)59.091 kJ·mol^-1远高于AB₅型合金的28.10 kJ·mol^-1。Ti_0.25V_0.34Nb_0.01Cr_0.10Ni_0.30合金电极的放电容量在303～343 K较宽的温度区间内随温度的升高而增加，且高温倍率放电(HRD)性能优于低温，当放电电流密度较大时，氢的扩散是放电过程的主要速度控制步骤。     

Stibene epoxidation with t-butyl hydroperoxide and hydrogen peroxide catalyzed by transition metal substituted heteropolytungstates

Tetra-n-butylammonium salts of transition metal-substituted heteropolytungstates, PW₁₁MO ₃₉ ^n– , catalyze the epoxidation of stilbenes by t-butyl hydroperoxide (M=Co^II, Mn^II, Cu^II, Ti^IV, Ru^IV, V^V, Nb^V) and hydrogen peroxide (M=Zr^IV) in acetonitrile. Epoxidation of cis-stilbene is non-stereospecific.     

Electrochemical Hydrogen Storage in Ti1.6V0.4Ni1−xCox Icosahedral Quasicrystalline Alloys

The discovery of the icosahedral phase (i‐phase) in rapidly quenched Ti_1.6V_0.4Ni_1?xCo_x (x=0.02–0.1) alloys is described herein. The i‐phase occurs in a similar amount relative to the coexisting β‐Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i‐phase is metastable. The electrochemical hydrogen storage performances of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement. A discharge capacity of 261.5 mA h g^?1 was measured in a Ti_1.6V_0.4Ni_0.96Co_0.04 alloy electrode at 30 mA g^?1 and 303 K and it is shown that an appropriate amount of Co element addition would enhance the cycling stability at the expense of high‐rate discharging ability.     

Investigation of the influence of nickel content on the correlation between the hydrogen equilibrium pressure for hydrogen absorbing alloys and the capacity of MH electrodes in open and closed cells

Two series of overstoichiometric AB_2.4 alloys [(Zr_0.35Ti_0.65)(V_1.33Cr_0.4Fe_0.27)_{2– x} Ni_{0.4+ x} and (Zr_0.5Ti_0.5)(V_0.8Mn_0.8Cr_0.4)_{2– x} Ni_{0.4+ x} ], differing in the Zr to Ti ratios in group A and the presence of Mn or Fe in group B, were examined to consider the influence of various amounts of nickel on the structural parameters following the sorption of hydrogen. To predict the electrochemical behaviour of the prepared alloys as negative electrodes for Ni-MH cells, the pressure-composition isotherms (PCT) determined for the gas/solid phase system were correlated with the electrochemical pressure-composition (EPC) isotherms estimated from the rest potential of the alloy electrode. For preliminary assessment of the practical usefulness of the prepared samples, the electrodes made of all the alloys were subjected to charge/discharge measurements in a half-cell in 6 M KOH solution and the discharge capacities were estimated. Of the alloys with Fe and Mn components, the samples (Zr_0.35Ti_0.65)(V_0.93Cr_0.28Fe_0.19Ni_1.0) and (Zr_0.5Ti_0.5)(V_0.68Mn_0.68Cr_0.34Ni_0.7) provided the highest capacities. These alloys were chosen for testing the charge/discharge cycleability in closed Ni-MH cells. The reversibility of the cell with the former sample decreased significantly around the 25th cycle, whereas the discharge capacity of the cell with the latter sample remained almost unchanged during 100 cycles of testing. Electronic Publication     

Sol-gel Synthesis and Electrochemical Performance of Li4-xMgxTi5-xZrxO12 Anode Material for Lithium-ion Batteries

The anode materials Li_4?xMg_xTi_5?xZr_xO₁₂ (x=0, 0.05, 0.1) were successfully synthesized by sol‐gel method using Ti(OC₄H₉)₄, CH₃COOLi·2H₂O, MgCl₂·6H₂O and Zr(NO₃)₃·6H₂O as raw materials. The crystalline structure, morphology and electrochemical properties of the as‐prepared materials were characterized by XRD, SEM, cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS) and charge‐discharge cycling tests. The results show that the lattice parameters of the Mg‐Zr doped samples are slightly larger than that of the pure Li₄Ti₅O₁₂, and Mg‐Zr doping does not change the basic Li₄Ti₅O₁₂ structure. The rate capability of Li_4?xMg_xTi_5?xZr_xO₁₂ (x=0.05, 0.1) electrodes is significantly improved due to the expansile Li⁺ diffusion channel and reduced charge transfer resistance. In this study, Li_3.95Mg_0.05Ti_4.95Zr_0.05O₁₂ represented a relatively good rate capability and cycling stability, after 400 cycles at 10 C, the discharge capacity retained as 134.74 mAh·g^?1 with capacity retention close to 100%. The excellent rate capability and good cycling performance make Li_3.95Mg_0.05Ti_4.95Zr_0.05O₁₂ a promising anode material in lithium‐ion batteries.     

Effect of Nb-doping on electrochemical stability of Li4Ti5O12 discharged to 0?V

Li₄Ti_4.95Nb_0.05O₁₂ is synthesized by a citric acid-assistant sol–gel method. X-ray diffraction (XRD) reveals that highly crystalline Li₄Ti_4.95Nb_0.05O₁₂ without any impurity is obtained. The electrochemical performances of the Li₄Ti_4.95Nb_0.05O₁₂ and the Li₄Ti₅O₁₂ in the range from 0 to 2.5 V are investigated. The Li₄Ti_4.95Nb_0.05O₁₂ presents a higher specific capacity and better cycling stability than the Li₄Ti₅O₁₂ due to the improved conductivity. The Li₄Ti_4.95Nb_0.05O₁₂ exhibits a capacity as high as 231.2 mAh g⁻¹ after 100 cycles, which is much higher than the Li₄Ti₅O₁₂ (111.1 mAh g⁻¹). The effect of Nb-doping on electrochemical performance of Li₄Ti₅O₁₂ discharged to 0 V has also been discussed.     

Surface characteristics of high corrosion resistant Ni–Nb–Zr–Ti–Ta glassy alloys for nuclear fuel reprocessing applications

This work firstly discovered that the Ni₆₀Nb₁₅Zr₅Ti₁₅Ta₅ metallic glass exhibits high corrosion resistance in boiling 6 N HNO₃ solutions with and without Cr⁶⁺ ions, which may be of great potential for nuclear fuel reprocessing applications. The high corrosion resistance of the alloy is due to the formation of the passive film composed exclusively of Nb⁵⁺ and Ta⁵⁺ cations after immersion in the solution without Cr⁶⁺ ions, and Nb⁵⁺, Ta⁵⁺ and Cr³⁺ cations after immersion in the solution with Cr⁶⁺ ions.