Pd修饰LaNi5贮氢电极的电催化脱氯性能

为提高对氯苯酚(4-CP)脱氯的有效性,采用化学沉积法制备了镧镍合金镀钯电极(Pd/LaNi₅),对其进行了X射线衍射(XRD)、扫描电子显微镜(SEM)和线性扫描伏安(LSV)表征。电催化实验结果表明Pd/LaNi₅电极显示了比LaNi₅电极和Pd/Ni电极更高的4-CP脱氯活性,在初始浓度0.1 mmol·L^-1、表观电流密度10 mA·cm^-2、pH 4.0和钯载量1.8 mg·cm^-2时,4-CP的脱氯率和电流效率分别达到77.3%和0.14%。基于物理化学表征,可以断定电化学脱氯活性的增强主要源于LaNi₅更好的储氢能力。     

6种二氯酚电催化还原脱氯:表观动力学过程比较

采用自制的钯/聚吡咯(十二烷基苯磺酸钠)/钛(Pd/PPy(SDBS)/Ti)电极对二氯酚(DCP)的6种同分异构体进行了电化学还原脱氯研究。探讨了脱氯电流、溶液初始pH和污染物初始浓度对2,5-DCP脱氯过程的影响。在脱氯电流5 mA、溶液初始pH 2.5、温度25℃、污染物初始浓度100 mg·L^-1的条件下对2,3-DCP、2,4-DCP、2,5-DCP、2,6-DCP、3,4-DCP和3,5-DCP的脱氯过程进行了比较。6种DCP的脱氯产物均以苯酚为主,有少量的单氯酚产生,脱氯反应速率常数依次为4.735×10^-2、4.609×10^-2、4.845×10^-2、4.317×10^-2、3.973×10^-2、3.770×10^-2 min^-1。推测DCP的降解速率受pK_a、质子化效应和溶液pH等因素的影响,降解难度由小到大依次为2,4-DCP< 2,3-DCP< 2,5-DCP< 2,6-DCP< 3,4-DCP< 3,5-DCP。     

Ni-Fe双金属对氯代苯酚催化还原脱氯的试验

分别采用Ni-Fe双金属体系和单一零价铁对氯代有机物2,4-二氯苯酚、2-氯苯酚和4-氯苯酚进行了催化还原脱氯的研究。结果表明:单一零价铁能够对氯代苯酚还原脱氯,但效率不高,通常在10%～25%。在镍的催化作用下,零价铁对氯代苯酚的还原脱氯效率大大提高。当零价铁加入量为60 g/L,硫酸镍为0.6 g/L,初始氯代苯酚的质量浓度在25 mg/L左右,反应初始pH值控制在偏酸性的条件下,还原脱氯效率可达到70%以上。氯代苯酚降解的准一级速率常数和降解率满足以下规律:4-氯苯酚大于2-氯苯酚大于2,4-二氯苯酚。     

Pd/Fe双金属对1,2,4-三氯苯的催化脱氯

采用Pd/Fe双金属体系对1,2,4-三氯苯（1,2,4-TCB）进行了快速催化还原脱氯的研究.结果表明,在钯的催化作用下,零价铁对1,2,4-TCB有较好的还原脱氯效率.当Pd/Fe双金属的钯化氯为0.06%时,催化剂用量为1g/40mL,反应1h后TCB的脱氯率可达99%.反应速率随钯化氯的提高而增加.反应在Pd/Fe表面进行,符合准一级反应,反应速率常数为0.0837min-1.TCB在催化脱氯的过程中先脱氯成为DCB,再依次脱氯为氯苯和苯.     

2-氯-5-三氯甲基吡啶电化学氢化脱氯合成2-氯-5-甲基吡啶

2-氯-5-三氯甲基吡啶（TCMP）选择性氢化脱氯制备2-氯-5-氯甲基吡啶（CCMP）或2-氯-5-甲基吡啶（CMP）在农药“吡虫啉”合成中具有重要应用价值。首先在弱酸性的甲醇/乙酸/水混合溶剂中研究了TCMP电化学脱氯合成CCMP或CMP的可行性;其次,研究了阴极材料和电解液组成对TCMP选择性脱氯反应的影响;最后,采用膜厚度极距的板框式电解槽分别研究了阴、阳极支持电解质对电解槽压和电流密度与底物浓度对脱氯反应效率的影响。实验结果表明,在弱酸性的甲醇/乙酸/水混合溶剂中,TCMP能在银网阴极上高选择性的氢化脱氯成CMP;CMP收率从高到低的阴极依次为：银> 铜> 锌> 铅> 钛> 石墨> 镍。阴阳极支持电解质从四丁基高氯酸铵分别换成乙酸锂和硫酸,电解槽压大幅度下降。降低电流密度和提高底物浓度有利于TCMP电化学氢化脱氯效率。在优化条件下（阴极液：含10%乙酸+5%水+0.2 mol·L^-1乙酸锂的甲醇溶液;阴极：银网;电流密度：333 A·m^-2;温度：30℃）,0.2 mol·L^-1 TCMP 能高效地转化为CMP（收率：91%）,电流效率可达54%,电解槽压大约为3.0 V。     

石墨烯修饰电极的制备及其降解2,3,4-三氯苯酚的研究

采用滴涂-电化学沉积方法制备了用石墨烯修饰的钯/石墨烯-萘酚/钛(Pd/Graphene-Nafion/Ti)电极,考察了石墨烯浓度、Nafion浓度、沉积电流及沉积时间对电化学性能的影响。然后对电极的电化学特性、表面形貌特征、催化剂颗粒的晶体结构、结合能等进行了测试。以初始质量浓度为100 mg/L的2,3,4-三氯苯酚(2,3,4-TCP)为例,对电极的电化学还原脱氯性能、脱氯产物、脱氯路径及电极的稳定性进行了考察。结果表明,电极的最佳制备条件为:石墨烯和Nafion的质量分数分别为0.04%和0.20%,镀钯电流和时间分别为20 m A和45 min。该条件下制备的电极的氢吸附峰电流值为-170 m A,电极表面为密集的棱锥状凸起的钯单质,其洛伦兹晶粒尺寸为19.7 nm。反应80 min即可实现2,3,4-TCP的完全去除和氯原子的完全脱除,电流效率为35.4%,苯酚是2,3,4-TCP脱氯后的主要产物,电极在重复使用10次后仍然具有良好的脱氯效果和稳定性。     

锌/银二元金属体系中五氯吡啶的电催化还原脱氯

研究了Zn/Ag二元金属体系对五氯吡啶的催化还原脱氯性能。实验考察了初始pH值、催化剂的投加量、反应温度等参数对反应的影响,在此基础上探讨了其脱氯机理。实验结果表明：反应温度为60℃时,单一锌粉能够对五氯吡啶进行还原脱氯生成四氯吡啶,但是收率不高,只有20%左右,在银的催化作用下,四氯吡啶收率得到了很大提高。当反应初始pH控制在弱酸条件下（5左右）,硝酸银浓度为10 g·L^-1时,反应3h后四氯吡啶收率可达到60%以上。在Zn/Ag双金属表面,五氯吡啶的脱氯反应符合一级反应,速率常数为0.0097 min^-1。     

Raney Ni高效催化氯酚类污染物还原脱氯降解

采用Raney Ni催化剂,选择50%乙醇-水（50/50,体积比）作为溶剂体系,考察了不同类型碱及其添加量对Raney Ni催化4-氯苯酚（4-CP）还原脱氯反应的影响。结果表明,强碱（NaOH和KOH）和Et₃N更有利于Raney Ni催化下还原脱氯反应的进行,而且当n(NaOH/Et₃N)∶n(4-CP)=1.1~2.2时,Raney Ni能够保持较高的催化活性,可以在30min内实现4-CP的彻底还原脱氯,并建立了Raney Ni-50%乙醇-水（50/50,体积比）-NaOH催化体系。将该体系应用于研究取代基对Raney Ni催化芳香氯代物还原脱氯的影响,研究表明,Raney Ni催化剂对4-CP和4-氯苯胺（4-CA）的还原脱氯具有较高的选择性。进一步将Raney Ni-50%乙醇-水（50/50,体积比）-1.5NaOH催化体系应用于高浓度氯酚工业危废的还原脱氯处理,发现在该催化体系中氯酚工业危废中的氯代有机污染物可以彻底还原脱氯,且催化剂可以至少重复使用5次。该催化体系可以有效、彻底地还原脱氯降解氯酚工业危废,对高浓度氯酚工业危废的还原脱氯降解具有良好的应用前景。     

Ni/Fe双金属降解CCl4、CHCl3和CH2Cl2的试验

在批试验条件下研究了Ni/Fe双金属对CCl4(CT)、CHCl3(TCM)和CH2Cl2(DCM)的还原性脱氯性能。结果表明:(1)Ni/Fe双金属可有效对CT和TCM脱氯,但对DCM没有脱氯效果;(2)Ni/Fe双金属对CT和TCM的降解反应均符合准一级反应动力学方程;(3)在相似的反应条件下,Ni/Fe双金属对CT和TCM的脱氯效果好于Fe0,且脱氯速度与Ni/Fe质量比在一定数值范围内成正比;(4)对CT和TCM脱氯的反应速率常数kSA相差10.98～16.60倍,说明Ni/Fe双金属对氯代程度高的CT脱氯快于对氯代程度低的TCM;(5)Ni/Fe双金属对CT脱氯过程产生TCM,不产生DCM,且随着反应时间的继续,产生的TCM也继续被降解;而Ni/Fe双金属对TCM脱氯并不逐级产生DCM;Fe0对CT脱氯不仅产生TCM,也产生DCM。     

Pd/Fe双金属对水中m-二氯苯的催化脱氯

引　言氯代芳烃及其衍生物化学性质稳定 ,易在生物体内累积 ,大多被列为美国EPA环境优先控制污染物 ,一旦进入环境将对人类及其生态环境造成长期威胁 .因此 ,氯代芳烃的治理技术日益引起全球的关注[1] .自 2 0世纪 80年代末提出金属铁屑用于地下水的原位修复以来[2 ,3] ,用Fe0 还原脱氯已成为一个非常活跃的研究领域 ,特别是应用于地下水修复方面的研究 .Fernando等[4～ 7] 将双金属催化剂用于有机氯的催化还原脱氯 ,Fe0 表面的Pd或Ni等金属加速了还原脱氯反应 ,脱氯速率比Fe0 体系快得多 .本研究利用Pd/Fe双金属对m DCB进行了催化还…     

Catalytic hydrodechlorination of hexachlorobenzene on carbon supported Pd-Ni bimetallic catalysts

The study of the catalytic activity of carbon supported Pd-Ni catalysts for the hydrodechlorination of hexachlorobenzene was carried out in the liquid phase. The degree of dechlorination was found proportional to the surface Pd concentration, which is enhanced by the segregation of this element at the surface of the bimetallic particles.

It is also shown that isolated Pd atoms located at the surface of Ni rich bimetallic particles are more active than those lying in larger ensembles.

Finally bimetallic Pd-Ni catalysts containing only between 20 and 50 Pd atom%, although less active than pure Pd, lead to 75% of useful compounds, i.e. benzene, mono and dichlorobenzene.     

Quartz crystal microbalance studies on electrochemical behavior of electrodeposited Pd-Ni alloys

Electrochemical quartz crystal microbalance (EQCM) was applied in studies on electrochemical behaviour of Pd-rich Pd-Ni alloys in basic solutions. The results were compared with those obtained for pure Pd and Ni electrodes. The EQCM frequency response accompanying the desorption of the absorbed hydrogen is strongly influenced by the stresses generated during this process and depends on the alloy composition and the initial content of the absorbed hydrogen. The latter effect is much more pronounced for Pd-Ni alloys than for pure Pd electrode. The gravimmetric analysis of the oxidation processes of Ni(II) compounds on Pd-Ni electrodes and the subsequent reduction of the products is also complicated by the stresses accompanying these processes.     

镍/铁二元金属催化降解水体中的莠去津和对氯苯酚

在一定反应条件下,考察了Ni/Fe二元金属对不同取代基上Cl原子的脱除特性。实验以莠去津和对氯苯酚(p-CP)为研究对象,在水溶液中进行了脱氯降解。结果表明,与金属Fe0相比,Ni/Fe对莠去津和p-CP均有明显的催化脱氯降解效果。单位比表面Ni/Fe对p-CP和莠去津的表观反应速率常数分别为:kSA=7.61×10-4(min-1.m-2)和k′SA=5.64×10-3(min-1.m-2),说明Ni/Fe对三氮苯环上Cl原子有更强的脱除特性。不同反应pH对Ni/Fe降解p-CP的影响比莠去津小,反应60 min,p-CP在pH=2.0、3.0、4.0和未调节pH条件下的脱氯效率分别为43%、44%、35%和28%;120 min分别为69%、62%、57%、48%。而莠去津在pH=4.0和未调节pH条件下几乎没有还原,主要是受氯化物本身性质的影响。另外,通过反应体系的电化学测试表明,在Ni/Fe催化还原莠去津和p-CP的过程中,反应中主要的还原剂是Fe0溶解产生并吸附在催化剂表面的H2。     

The use of a carbonized phenolic formaldehyde resin coated Ni foam as an interlayer to increase the high-temperature strength of C/C composite-Nb brazed joints

A novel carbonized phenolic formaldehyde resin (PF) resin-coated Ni foam was used as an interlayer for brazing carbon fiber reinforced carbon composites (C/C) and Nb using a Ti–Ni filler. At first, uniformly distributed carbonaceous laminae with different mass fractions on the Ni foam surface were acquired after the carbonization process by controlling the concentration of the PF solution. Afterwards, the obtained carbonaceous laminae covered Ni foam composite (C-Ni_f) was applied as an interlayer for brazing C/C and Nb via an assembly of C/C/Ti foil/Ni foil/C-Ni_f interlayer/Ti foil/Nb. The morphologies and microstructures of the carbonization product and the interfacial microstructures of the joints were investigated. The brazing mechanism has been elaborated in detail. With the help of the interconnected porous structure of the Ni foam, the distribution of the in-situ formed (Ti,Nb)₂Ni particles, (Ti,Nb)C ring reinforcements as well as the Nb solid solution were uniformly obtained throughout the brazing seam. As a result, the joint residual stress was effectively released and consequently, the joint shear strength at elevated temperature (1000 °C) reached up to 33 MPa, which is 4.5 times higher than the directly brazed joint without an interlayer.     

The study of hydrogen electrosorption in layered nickel foam/palladium/carbon nanofibers composite electrodes

In the present work, the process of hydrogen electrosorption occurring in alkaline KOH solution on the nickel foam/palladium/carbon nanofibers (Ni/Pd/CNF) composite electrodes is examined. The layered Ni/Pd/CNF electrodes were prepared by a two-step method consisting of chemical deposition of a thin layer of palladium on the nickel foam support to form Ni/Pd electrode followed by coating the palladium layer with carbon nanofibers layer by means of the CVD method. The scanning electron microscope was used for studying the morphology of both the palladium and carbon layer. The process of hydrogen sorption/desorption into/from Ni/Pd as well as Ni/Pd/CNF electrode was examined using the cyclic voltammetry method. The amount of hydrogen stored in both types of composite electrodes was shown to increase on lowering the potential of hydrogen sorption. The mechanism of the anodic desorption of hydrogen changes depending on whether or not CNF layer is present on the Pd surface. The anodic peak corresponding to the removal of hydrogen from palladium is lower for Ni/Pd/CNF electrode as compared to that measured for Ni/Pd one due to a partial screening of the Pd surface area by CNF layer. The important feature of Ni/Pd/CNF electrode is anodic peak appearing on voltammetric curves at potential ca. 0.4 V more positive than the peak corresponding to hydrogen desorption from palladium. The obtained results showed that upon storing the hydrogen saturated Ni/Pd/CNF electrode at open circuit potential, diffusion of hydrogen from carbon to palladium phase occurs due to interaction between carbon fibers and Pd sites on the nickel foam support.     

电化学还原脱氯用GC负载Pd-Ni电极的制备及表征

通过电沉积法在玻碳板（GC）电极上负载钯镍双金属颗粒,并利用正交实验对其进行循环伏安（CV）研究,得到Pd-Ni/GC电极的最佳制备条件为：Ni²⁺=8.5 mmol·L^-1,Pd²⁺=3 mmol·L^-1,pH=7.0,J_k=15 mA·cm^-2,T=30 min。可以在-500 mV（以Hg/Hg₂SO₄为参比电极）左右获得-24.83 mA的氢吸附峰。用聚吡咯(PPy)修饰GC制备Pd-Ni/PPy/GC电极,CV结果表明,Pd-Ni/PPy/GC电极具有比Pd-Ni/GC电极更大的氢吸附峰值,可以在-500 mV（以Hg/Hg₂SO₄为参比电极）左右获得-32.33 mA的氢吸附峰。扫描电镜（SEM）分析表明,聚吡咯的修饰明显改变了Pd-Ni颗粒的沉积形态,使其沉积粒径更小,分散度更高。     

The additive-free electrode based on the layered MnO2 nanoflowers/reduced,graphene oxide film for high performance supercapacitor

The MnO₂ nanoflowers/reduced graphene oxide composite is coated on a nickel foam substrate (denoted as MnO₂ NF/RGO @ Ni foam) via the layer by layer (LBL) self-assembly technology without any polymer additive, following the soft chemical reduction. The layered MnO₂ NF/RGO composite is uniformly anchored on the Ni foam skeleton to form the 3D porous framework, and the interlayers have access to lots of ions channels to improve the electron transfer and diffusion. This special construction of 3D porous structure is beneficial to the enhancement of electrochemical property. The specific capacitance is up to 246 F g⁻¹ under the current density of 0.5 A g⁻¹. After 1000 cycles, it can retain about 93%, exhibiting excellent cycle stability. The electrochemical impedance spectroscopy measurements confirm that MnO₂ NF/RGO @ Ni foam electrode has lower R_ESR and R_CT values when compared to MnO₂ @ Ni foam and RGO @ Ni foam. This study opens a new door to the preparation of composite electrodes for high performance supercapacitor.     

Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

We have successfully prepared a series of Pd-Ni/TiO₂ catalysts by a one-step impregnation-reduction method. Among these catalysts with different compositions of Ni and Pd, the one with the Ni:Pd ratio of 2.95 showed the best activity. Small monodispersed Pd-Ni bimetallic nanoparticles were loaded on the surface of titanium oxide nanopowder as confirmed with TEM and EDS mapping. The XPS analysis demonstrated that Pd exists as 31% Pd(II) species and 69% Pd(0) species and all nickel is Ni(II). The prepared Pd-Ni/TiO₂ exhibited enhanced catalytic activity compared to an equal amount of Pd/TiO₂ for Suzuki-Miyaura reactions together with excellent applicability and reusability.

Open image in new window

     

复合电沉积制备TiO_2/泡沫镍光催化材料及其催化活性

采用复合电沉积方法制备了TiO2/泡沫镍光催化材料,通过扫描电子显微镜（SEM）和能量色散谱（EDS）分别对纳米复合镀层进行了形貌和成分表征,同时研究了在镀液中添加不同表面活性剂对光催化材料镀层的影响。讨论了TiO2/泡沫镍光催化材料对大肠杆菌和小球藻的光催化活性。结果表明：在本实验的电沉积工艺条件下,泡沫镍基底上获得了微粒分布均匀、Ti的质量分数为5.97%的纳米TiO2-Ni复合沉积层。添加了阴离子表面活性剂的光催化材料表面TiO2颗粒具有良好的分散性。TiO2/泡沫镍光催化材料处理含大肠杆菌水样,反应30 min灭活率达到60.1%,反应2 h灭活率达到99.9%;处理水中的小球藻溶液,初始3 h内,小球藻溶液中所含叶绿素a从初始的98.2 mg/m3降至38.2 mg/m3。