镍锡析氢活性阴极的电化学制备及其在碱性溶液中的电催化机理

采用恒电流电沉积法在铜箔基底上获得镍锡合金镀层电极. 电子能谱(EDS)、X射线衍射(XRD)以及高分辨透射电镜(HRTEM)分析表明, 随着锡含量的增加, 镀层由镍晶胚与非晶镍锡构成的非晶态结构转变为Ni₃Sn₄与Ni₃Sn₂的混晶结构. 扫描电镜(SEM)分析发现, 非晶结构镍锡合金电极表面粒子分布均匀且粒径细小, Ni₃Sn₄与Ni₃Sn₂混晶结构的镍锡合金电极表面粗糙且断面呈分层自组装结构. 在25℃, 1 mol·L^-1 NaOH溶液中的稳态极化曲线表明非晶结构的镍锡合金电极具有良好的催化活性, 其析氢过电位仅为85 mV. 交流阻抗测试表明, 非晶以及混晶结构的镍锡合金在析氢电催化反应过程中由电化学吸附(Volmer)以及电化学脱附(Heyrovsky) 两个电荷转移过程控制, 且非晶结构电极相比于Ni₃Sn₄与Ni₃Sn₂混晶结构电极的高活性源于其活性氢具有更快的电化学吸附以及脱附速度.     

镍-镧合金的电沉积及其晶化行为与析氢性能

在尿素-溴化钠熔体中电沉积Ni-La合金,考察了合金的沉积行为和阴极电流密度对合金组成和表面形貌的影响。结果表明,镧与镍经过诱导共沉积形成Ni-La合金;随着阴极电流密度的增加,镀层中镧含量先升高后降低（在15 mA·cm^-2条件下达到最高）,镀层表面微粒变大。用热分析技术和X射线衍射研究了Ni89.7La10.3合金的晶化行为,该合金在镀态时呈非晶态结构,在446.1℃热处理后的镀层晶化生成面心立方Ni-La相（Fm3m）。采用电化学技术研究了该镀层的电催化析氢性能,实验证实Ni89.7La10.3合金的电催化析氢性能优于镍。     

电沉积纳米镍合金在海水溶液中的析氢性能

采用电沉积法获得Ni、Ni-Fe和Ni-Fe-C合金镀层电极, 在90 °C模拟海水(0.5 mol·L-1 NaCl, pH=12)的稳态极化曲线表明Ni-Fe-C合金电极具有最好的析氢催化性能. 通过扫描电子显微镜(SEM)观察电极表面形貌、X射线衍射(XRD)与透射电子显微镜(HRTEM)分析合金的晶体结构, 发现电极材料的晶粒尺寸影响析氢催化性能, 晶粒尺寸越小析氢催化活性越好. 用电化学阻抗方法(EIS)研究电极析氢催化性能的本质原因, 结果表明电极表面活性点数目和电极的本质电催化活性对合金电极析氢催化活性有重要的影响.     

电沉积纳米镍合金在模拟海水溶液中的析氢性能

采用电沉积法获得Ni、Ni-Fe和Ni-Fe-C合金镀层电极,在90℃模拟海水(0.5mol·L-1NaCl,pH=12)的稳态极化曲线表明Ni-Fe-C合金电极具有最好的析氢催化性能.通过扫描电子显微镜(SEM)观察电极表面形貌、X射线衍射(XRD)与高分辨透射电子显微镜(HRTEM)分析合金的成分和晶体结构,发现电极材料的晶粒尺寸影响析氢催化性能,晶粒尺寸越小析氢催化活性越好.用电化学阻抗方法(EIS)研究电极析氢催化性能的本质原因,结果表明电极表面活性点数目和电极的本质电催化活性对合金电极析氢催化活性有重要的影响.     

退火前后镍钨硼合金电沉积层的结构与性能

采用电化学技术、XPS、DSC、XRD等方法研究Ni W B合金电沉积及热处理前后合金镀层的结构和显微硬度.结果表明,在Ni W B合金电沉积过程中伴随着化学沉积镍等过程以及Na2B4O7在镀层中的夹杂;Ni W和Ni W B合金电沉积层分别表现为纳米晶结构和非晶态结构;热处理过程中合金电沉积层发生晶粒粗化过程以及Ni W B合金镀层发生新相形成过程,产生Ni4W和镍硼化物如Ni2B、Ni3B等沉淀物;400 ℃热处理2 h后Ni W合金镀层有最大的显微硬度达919.8 kg•mm－2,而在500 ℃下Ni W B合金有最大的硬度达1132.2 kg•mm－2.     

电沉积Ni/LaNiO3复合电极及其在碱性介质中的析氧性能

采用溶胶-凝胶法制备了钙钛矿型复合氧化物LaNiO3,然后将其加入瓦特镀镍液中进行复合电沉积,研究了镀液pH值和阴极电流密度对Ni/LaNiO3复合镀层组成的影响。运用扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等对复合镀层进行表征,结果表明:最佳电沉积工艺条件是镀液pH=5.8和阴极电流密度jk=90 mA.cm-2,所得的Ni/LaNiO3复合镀层中LaNiO3的质量含量约为60%。用循环伏安、稳态极化、恒电位阶跃、电化学阻抗谱等电化学技术评价了Ni/LaNiO3复合电极的析氧性能。结果表明:在5 mol.L-1的KOH溶液中,Ni/LaNiO3复合电极的起始析氧电位较镍电极负,表观活化自由能比镍电极降低约2/3,比表面积约为镍电极的55倍,析氧电催化性能得到大幅度提高。     

Ni/NiCo2O4复合电极的制备及其在碱性介质中的析氧性能

采用共沉淀法制备尖晶石型复合氧化物 NiCo2O4, 然后将其加入瓦特镀镍液中, 复合电沉积了 Ni/NiCo2O4复合镀层. 通过改变镀液pH值、阴极电流密度jk等条件, 探索复合电沉积的最佳工艺条件. 运用扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)表征了复合镀层的表面形貌、颗粒含量和结构. 结果表明: 在镀液pH=6.2和jk=100 mA·cm-2的条件下所得Ni/NiCo2O4复合镀层中, NiCo2O4的含量达到最高(30.6%,w). 在5 mo·lL-1的KOH溶液中, 采用循环伏安、稳态极化和电化学阻抗法研究了电极的电催化析氧性能. 与镍电极对比, Ni/NiCo2O4复合电极的电催化析氧性能更高, 表观活化自由能降低了53.2 kJ·mol-1, 其析氧反应的表观交换电流密度是镍电极的7倍. 电化学阻抗谱分析表明, Ni/NiCo2O4复合电极在碱性溶液中析氧反应由电化学步骤和扩散步骤联合控制. 恒电位长时间电解析氧实验表明, 该Ni/NiCo2O4复合电极在碱性溶液中的析氧具有高的稳定性.     

Ni/PdO/RuO_2复合型活性阴极的制备与表征

采用热分解氧化法,在Ni基体上制备以PdO为中间层、RuO2为活性层的Ni/PdO/RuO2复合型活性阴极,并通过XPS、XRD、能量色散X荧光(EDXRF)、SEM、极化曲线、循环伏安法和交流阻抗谱等表征其组成、结构与电化学性能。结果表明,Pd和Ru分别以PdO和RuO2的形式存在于Ni/PdO/RuO2复合型活性阴极中,其含量分别为1.25wt%和1.71wt%;在363K、11mol·L-1NaOH溶液、3kA·m-2电流密度下,Ni/PdO/RuO2复合型活性阴极的析氢过电位比Ni电极和Ni/RuO2电极分别低371和125mV;循环伏安法循环72h后,该复合型活性阴极双电层电容值减小30.6%,比Ni/RuO2电极表层结构更稳定;Ni/PdO/RuO2复合型活性阴极的表面粗糙度大且无明显的裂纹存在,与纯镍电极相比,该复合型活性阴极比表面积增加了31.12倍。     

Ni/Ag2O/RuO2-Pt阴极制备与析氢性能

以三氯化钌和氯铂酸为源物质,用溶胶凝胶法制备Ni/Ag2O/RuO2-Pt复合阴极,研究了不同涂覆液AgNO3浓度和热处理温度对该阴极析氢性能的影响.采用SEM-EDS、XRD和XPS观察阴极的表面形貌、表征其组分,结果表明,Ni/Ag2O/RuO2-Pt复合阴极表面致密,粗糙度大且裂纹少.电化学测量表明,在11 mol.L-1NaOH(90℃)溶液、0.3 A.cm-2电流密度下,Ni/Ag2O/RuO2-Pt复合阴极的析氢电位比纯Ni电极正移484 mV;交换电流密度是纯Ni电极的10倍.该阴极制备工艺简单,析氢活性高,有望降低氯碱工业的能耗.     

重稀土元素对非晶态NiB合金催化剂性能的影响

用脉冲微反技术以苯加氢反应为探针，研究了重稀土元素Dy，Ho，Er，Tm，Yb，Lu对非晶态NiB合金催化剂的加氢和抗硫性能的影响。用X射线衍射(XRD)、差示扫描量热(DSC)，CO化学吸附法、程序升温还原(TPR)及程序升温脱附(TPD)等方法对催化剂进行了表征。结果表明，重稀土可提高NiB合金的热稳定性、活性和抗硫性。其原因为稀土RE对NiB合金的电子及几何效应共同作用的结果导致活性中心数增多、活性镍表面积增大，吸氢量明显增大而吸氢强度变弱；同时降低了非晶态NiB合金催化剂催化的苯加氢反应的活化能。非晶态NiB和NiBRE合金催化剂上有4种氢吸附中心，其中3种吸附中心参与了表面反应。     

Ni-Fe/Ti和Ni-Fe-S/Ti的制备及其电催化水分解性能

以钛网为基底,采用电沉积法制备了Ni-Fe/Ti析氧电极,然后将得到的Ni-Fe/Ti电极通过固相硫化制备了Ni-Fe-S/Ti析氢电极. 分别考察了电沉积液中Ni ²⁺/Fe ³⁺离子摩尔浓度比和硫脲加入量对Ni-Fe/Ti和Ni-Fe-S/Ti结构和电化学性能的影响. 结果表明,随着电沉积液中Ni ²⁺含量的增加,Ni-Fe/Ti电极析氧性能先增强后减弱,Ni9Fe1/Ti电极具有最好的析氧性能;随着硫脲加入量的增加,Ni-Fe-S/Ti电极析氢性能呈现先增强后减弱的趋势,Ni9Fe1S0.25/Ti电极具有最好的析氢性能. 在50 mA·cm ^-2下,Ni9Fe1/Ti电极的析氧过电位为280 mV,Ni9Fe1S0.25/Ti电极的析氢过电位为269 mV,且均具有很好的稳定性. 将Ni9Fe1/Ti与Ni9Fe1S0.25/Ti分别作为阳极和阴极进行电催化全水分解,电流密度达到50 mA·cm ^-2所需电势仅1.69 V,表现出很好的全水解催化性能.     

非晶态Ni-S-Mn三元合金电极析氢行为

非晶态Ni-S-Mn三元合金电极析氢行为;电极;析氢电催化活性;水电解;非晶态合金     

Transmission electron microscopy and X-Ray diffraction analysis of aluminum-induced crystallization of amorphous silicon in alpha-Si:H/Al and Al/alpha-Si:H structures.

Solid phase crystallization of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (alpha-Si:H) in alpha-Si:H/Al and Al/alpha-Si:H structures has been investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Radiative heating has been used to anneal films deposited on carbon-coated nickel (Ni) grids at temperatures between 200 and 400 degrees C for TEM studies. alpha-Si:H films were deposited on c-Si substrates using high vacuum (HV) PECVD for the XRD studies. TEM studies show that crystallization of alpha-Si:H occurs at 200 degrees C when Al film is deposited on top of the alpha-Si:H film. Similar behavior was observed in the XRD studies. In the case of alpha-Si:H deposited on top of Al films, the crystallization could not be observed at 400 degrees C by TEM and even up to 500 degrees C as seen by XRD.     

纳米多孔Ni、Ni3S2/Ni复合电极的制备及其电催化析氢性能

采用脱合金化和水热合成的方法制备纳米多孔Ni和纳米多孔Ni₃S₂/Ni复合电极。通过N2吸附-脱附测试、XRD、SEM、TEM等方法表征电极的孔径分布、物相和微观结构。在1 mol·L^-1的NaOH溶液中,运用线性扫描伏安(LSV)曲线、交流阻抗(EIS)谱图、恒电流电解法等测试电极的电催化析氢性能。结果表明:在电流密度为50 mA·cm^-2时,与纳米多孔Ni相比,Ni₃S₂/Ni合金具有更低的析氢过电位以及更高的析氢活性,同时纳米多孔Ni₃S₂/Ni复合电极具有更低表观活化能和电子转移阻抗,进一步明确了过渡金属硫化物对电催化析氢性能的特殊贡献。     

纳米多孔Ni、Ni3S2/Ni复合电极的制备及其电催化析氢性能

采用脱合金化和水热合成的方法制备纳米多孔Ni和纳米多孔Ni₃S₂/Ni复合电极。通过N₂吸附-脱附测试、XRD、SEM、TEM等方法表征电极的孔径分布、物相和微观结构。在1 mol·L^-1的NaOH溶液中,运用线性扫描伏安（LSV）曲线、交流阻抗（EIS）谱图、恒电流电解法等测试电极的电催化析氢性能。结果表明：在电流密度为50 mA·cm^-2时,与纳米多孔Ni相比,Ni₃S₂/Ni合金具有更低的析氢过电位以及更高的析氢活性,同时纳米多孔Ni₃S₂/Ni复合电极具有更低表观活化能和电子转移阻抗,进一步明确了过渡金属硫化物对电催化析氢性能的特殊贡献。     

Thermodynamic analysis of (Ni,Fe)3Al formation by mechanical alloying

(Ni, Fe)₃Al intermetallic compound was synthesized by mechanical alloying (MA) of Ni, Fe and Al elemental powder mixtures of composition Ni₅₀Fe₂₅Al₂₅. Phase transformation and microstructure characteristics of the alloy powders were investigated by X-ray diffraction (XRD). The results show that mechanical alloying resulted in a Ni (Al, Fe) solid solution. By continued milling, this structure transformed to the disordered (Ni, Fe)₃Al intermetallic compound. A thermodynamic model developed on the basis of extended theory of Miedema is used to calculate the Gibbs free-energy changes. Final product of MA is a phase having minimal Gibbs free energy compared with other competing phases in Ni–Fe–Al system. However in Ni–Fe–Al system, the most stable phase at all compositions is intermetallic compound (not amorphous phase or solid solution). The results of MA were compared with thermodynamic analysis and revealed the leading role of thermodynamic on the formation of MA product prediction.     

Synthesis and performance of electroless Ni–P–TiCN composite coatings on Al substrate

Electroless Ni–P and Ni–P–TiCN composite coatings have been deposited successfully on Al substrates. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) techniques were applied to study the surface morphology and the chemical composition of the deposited films. Moreover, X‐ray diffraction (XRD) proved that Ni–P and Ni–P–TiCN deposits have amorphous structures. The properties of Ni–P–TiCN/Al composite films such as hardness, corrosion resistance and electrocatalytic activity were examined and compared with that of Ni–P/Al film. The results of hardness measurements reveal that the presence of TiCN particles with Ni–P matrix improves its hardness. Additionally, the performance against corrosion was examined using Tafel lines and electrochemical impedance spectroscopy techniques in both of 0.6 M NaCl and a mixture of 0.5 M H₂SO₄ with 2 ppm HF solutions. The results indicate that the incorporation of high dispersed TiCN particles into Ni–P matrix led to a positive shift of the corrosion potential and an increase in the corrosion resistance for all aluminum substrates after their coating with Ni–P–TiCN. In addition, Ni–P–TiCN/Al electrodes showed a higher electrochemical catalytic activity and stability toward methanol oxidation in 0.5 M NaOH solution compared with that of Ni–P/Al. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and crystal structure of a Pr5Ni19 superlattice alloy and its hydrogen absorption-desorption property

The intermetallic compound Pr(5)Ni(19), which is not shown in the Pr-Ni binary phase diagram, was synthesized, and the crystal structure was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two superlattice reflections with the Sm(5)Co(19)-type structure (002 and 004) and the Pr(5)Co(19)-type structure (003 and 006) were observed in the 2θ region between 2° and 15° in the XRD pattern using Cu Kα radiation. Rietveld refinement provided the goodness-of-fit parameter S = 6.7 for the Pr(5)Co(19)-type (3R) structure model and S = 1.7 for the Sm(5)Co(19)-type (2H) structure model, indicating that the synthesized compound has a Sm(5)Co(19) structure. The refined lattice parameters were a = 0.50010(9) nm and c = 3.2420(4) nm. The high-resolution TEM image also clearly revealed that the crystal structure of Pr(5)Ni(19) is of the Sm(5)Co(19) type, which agrees with the results from Rietveld refinement of the XRD data. The P-C isotherm of Pr(5)Ni(19) in the first absorption was clearly different from that in the first desorption. A single plateau in absorption and three plateaus in desorption were observed. The maximum hydrogen storage capacity of the first cycle reached 1.1 H/M, and that of the second cycle was 0.8 H/M. The 0.3 H/M of hydrogen remained in the metal lattice after the first desorption process.     

LiCl-KCl-LaCl3熔盐体系中La(III)的电化学行为

在773 K条件下,研究了La（III）在LiCl-KCl熔盐中W和Ni电极上的电化学行为。La（III）还原反应是一步三电子转移的准可逆反应;通过在Ni电极上直接电沉积La的方法可以获得La-Ni金属间化合物;恒电位电解可以获得含三种金属间化合物（LaNi₅、La₇Ni₁₆和La₂Ni₃）的La-Ni合金层,并且通过X射线衍射仪（XRD）和扫描电镜-能谱分析仪（SEM-EDS）确定物相并表征结构。采用开路计时电位法估算了LaNi₅金属间化合物的标准生成吉布斯自由能。揭示了恒电位电解方法是制备La-Ni镀层合金以及提取熔盐中La的有效方法。