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1.
贮氢合金电极在山梨醇制备中的应用 总被引:1,自引:0,他引:1
用贮氢合金作催化还原电极恒电位电解葡萄糖 ,得出合金的表面处理及电极的活化可提高山梨醇电流效率至 80 %以上的结论。同时贮氢电极与Pb电极及发泡Ni电极作了对比 ,发现电解葡萄糖制备山梨醇过程中 ,贮氢电极是较好的还原电极。用贮氢电极 (2 )做阴极 ,30℃ ,电流密度为 80 0mA/dm2 ,葡萄糖溶液及硫酸钠支持电解质浓度均为 0 .5mol/L ,pH =8的条件下 ,电解葡萄糖制山梨醇电流效率高达 94% ,葡萄糖转化率达 80 %以上。 相似文献
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MlNi5-x(CoMnAl)x催化丁腈橡胶双键加氢研究 总被引:1,自引:1,他引:0
贮氢合金MlNi5-x(CoMnAl)x通常用作氢电池的电极材料。笔者则对其氢化物作为催化剂和氢源催化丁腈橡胶溶液加氢进行了详细研究:结果表明,对合金的表面处理与否以及表面处理方式部对合金氢化物的催化活性有重要影响,其中不作任何表面处理的合金对丁腈橡胶溶液加氢氢化度为0;而各种不同表面处理方式中以先经6moL/L KOH处理,再用质量分数为1%的KBH4浸泡的合金活性最好。试验还表明以Pd、Pt等金属进行表面修饰,可使合金氢化物催化加氢活性提高。同时研究了表面积对合金催化活性的影响,研究显示,经反复充一放氢或球磨可有效提高合金比表面,催化加氢产物氢化度也随之提高。 相似文献
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镍钼合金镀层用于电极表面处理能提高其析氢催化性能。采用Taguchi试验设计镍钼合金电镀工艺。阐述了Taguchi设计方法的原理,通过正交试验优出一种镍钼合金电镀的最佳工艺,大大降低了镍钼合金镀层的析氢性能。 相似文献
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系统研究了工作温度(T=25,35,45,55℃)对V基固溶体型贮氢合金TiV_(2.1)Ni_(0.4)电化学性能的影响。XRD及SEM分析表明,TiV_(2.1)Ni_(0.4)由体心立方(bcc)结构的V基固溶体主相和TiNi基第二相组成。电化学测试表明,当工作温度升高时,合金的活化性能得到改善,最大放电容量显著提高,循环稳定性明显降低。同时,ICP分析表明,高温下碱液中Ti和V元素的大量溶出,是导致合金循环容量衰退的主要原因。随着温度的增加,合金电极的交换电流密度I_o和极限电流密度I_L增大,电极表面的反应阻抗减小,合金高倍率放电性能得到改善。 相似文献
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研究了氟处理对La_(1.8)Ca_(0.2)Mg_(14)Ni_3合金的吸放氢性能影响。结果表明,用NH_4F溶液处理的合金有更为优越的初始吸氢性能。在没有活化的情况下,处理的合金可在室温下部分吸氢,20min内可达到1.92%(质量分数);完全活化后,在453K时就呈现极好的吸氢性能,能在3min内吸氢3.88%(质量分数)。XRD分析表明,La_(1.8)Ca_(0.2)Mg_(14)Ni_3是由La_2Mg_(17)、Mg_2Ni、LaNi_(2.28)以及CaMg_2等相组成,氟处理后发现有新相MgF_2的存在。认为正是此新相的生成导致了氟处理前后合金的吸氢动力学性能的巨大变化。用SEM图分析合金的表面形貌的变化。 相似文献
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综述了La-Mg-Ni系贮氢合金电极的研究进展,包括合金材料的组成、结构、制备方法及表面处理工艺等,着重介绍了AB3型和A2B7型合金的电化学性能,分析讨论了各种替代元素对合金性能影响的原因,提出了未来La-Mg-Ni系贮氢合金应用研究的方向。 相似文献
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采用感应熔炼法制备La0.75Mg0.25Ni3.4-xAl0.1Cox (x=0.0, 0.5, 1.0)贮氢合金,研究了合金元素Co对Ni部分替代对合金相结构及电化学性能的影响. 结果表明,合金由La2Ni7相、LaNi5相及LaMg2Ni9相组成. 随Co含量的增加,合金电极活化次数变化不大,最大放电容量、循环稳定性呈现先增后减的趋势. 合金的最大放电容量和循环保持率分别由x=0时的316.92 mA.h/g和61.83%增加到x=0.5时的340.31 mA.h/g和75.21%,而后减少到x=1.0时的333.22 mA.h/g和66.70%. 而合金的高倍率放电性能降低,当放电电流密度为900 mA/g时,其倍率放电性能由62.49% (x=0)减小到53.68% (x=1.0). 合金电极的极限电流、贮氢合金电化学反应电阻逐渐增大,其高倍率放电性能的降低源于电极表面的电子迁移速率和氢在合金体相中扩散速率的共同作用. 相似文献
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储氢合金是影响镍氢电池性能的主要因素,对储氢合金进行表面处理可以有效提高镍氢电池的性能。本文对储氢合金表面进行包覆镍硼合金处理,通过扫描电镜(SEM)及X射线衍射分析(XRD)对电极表面进行了表征,测定了包覆前后镍氢电池的大电流放电性能,以交流阻抗法和循环伏安法对电极进行了评价。结果表明,包覆镍硼合金后,电化学阻抗减小,电极的大电流放电性能有所提高,循环寿命增长,对储氢合金表面包覆镍硼合金可有效提高镍氢电池性能。 相似文献
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The codeposition kinetics of copper and nickel alloys in complexing citrate ammonia electrolytes has been investigated by means of polarization and electrochemical impedance techniques. It is confirmed that the two-step discharge of the complexed cupric species Cu(II)Cit is diffusion-controlled during the alloy deposition, resulting in an increase in the nickel content of the alloy with electrode polarization. Impedance spectra are also consistent with a two-step discharge of Ni(II) cations involving an intermediate adsorbate, Ni(I)ads, originating from the reversible first step. A reaction model is developed for the parallel discharge of Cu(II)Cit and Ni(II) in which the reactions for nickel deposition are catalysed by active sites permanently renewed at the surface of the growing alloy. The surface density of these sites, slowly nucleated from Ni(I)ads and included in the deposit, varies with the electrode polarization, thus generating a low-frequency feature specific of Cu–Ni codeposition. This reaction model reproduces to a reasonable extent the potential dependence of the partial current densities for nickel and copper discharge, the current dependence of the alloy nickel content and also most of the experimental relaxation processes observed on impedance spectra.Nomenclature
b
1,b
2,b
3,b
3
b
4,b
5,b
7
Tafel coefficients (V–1)
-
C
concentration of Cu(II)Cit at distancex (mol cm–3)
- [Cu(II)]
bulk concentration of Cu(II)Cit (mol cm–3)
-
C
0
concentration of Cu(II)Cit atx=0 (mol cm–3)
-
C*
concentration of Cu(I)Cit atx=0 (mol cm–3)
- C
0, C*
variations inC
0,C* due to E
-
(Cu), (Ni)
molecular weights (g)
-
C
dl
double layer capacitance (F cm–2)
-
D
diffusion coefficient of Cu(II)Cit (cm2 s–1)
-
E
electrode potential (V)
-
f
frequency (s–1)
-
F
Faraday (constant 96 487 A s mol–1)
-
g
interaction factor between adsorbates
-
i,i
Cu,i
Ni
current densities (A cm–2)
- Im(Z)
imaginary part ofZ
-
j
(–1)1/2
-
k
mass transfer coefficients (cm s–1)
-
K
1,K
3
rate constants (cm s–1)
-
K
2
rate constants (s–1)
-
K
3,K
4,K
5,K
6,K
7
rate constants (cm–2 s–1)
- [Ni(II)]
bulk concentration of NiSO4 (mol cm–3)
-
R
t
charge transfer resistance ( cm2)
- Re(Z)
real part ofZ
-
t
time (s)
-
x
distance from the electrode (cm)
-
Z
F
faradaic impedance ( cm2)
-
Z
electrode impedance
-
maximal surface concentration of Ni(I)ads intermediates (mol cm–1)
-
nickel content in the deposited alloy (wt %)
-
thickness of Nernst diffusion layer (cm)
- 1
electrode coverage by adsorbed Ni(I)ads intermediate
- 2
electrode coverage by active sites
- 1, 2
variations in 1, 2 die to E
- *
=K
2
–1
(s)
- d
diffusion time constant (s)
- 1
time constant relative to 1 (s)
- 2
time constant relative to 2 (s)
-
angular frequency (rad s–1)
-
electrode rotation speed (rev min–1) 相似文献
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C.-O.A. Olsson 《Electrochimica acta》2003,48(27):3999-4011
Anodisation of a Nb-Zr alloy was studied in ammonium sulphate and hydrochloric acid electrolytes using electrochemical and surface analysis methods. Using electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry, a value of εr=27 was estimated for the relative permittivity and of 0.4 V nm−1 for the electrical field in the oxide film. Annealing of a mechanically polished disc sample to 600 °C for 14 h in UHV resulted in a fourfold surface enrichment of zirconium. This enrichment remained after anodisation in the sulphate solution, but could be removed with an anodisation in hydrochloric acid. Auger electron spectroscopy was used to estimate the thickness and composition of the anodic oxides. The film thickness measurements suggested a logarithmic growth law. The surface concentration of zirconium at the outer film surface of heat-treated samples decreased logarithmically when anodisation was performed in 1 M hydrochloric acid. No corresponding decrease in zirconium concentration was observed during immersion at open circuit. 相似文献
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Catalloy工艺可生产出真正的合金化聚合物材料,是聚烯烃合金革命化的技术.本文介绍这种工艺的发展过程及应用. 相似文献