Preparation and characterization of palladium/polypyrrole-reduced graphene oxide/foamed nickel composite electrode and its electrochemical dechlorination of triclosan

In this study, a new composite electrode of palladium (Pd) nanoparticles dispersed on polypyrrole-reduced graphene oxide (PPy-rGO) loaded on foam-nickel was achieved by galvanostatic method. Characterization of structures, morphology and crystallinity of the synthesized materials were investigated by scanning electron microscopes (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results of XPS and XRD demonstrated Pd showed primarily as Pd0. From SEM and TEM results, we had seen that Pd nanoparticles were dispersible well on the composite electrode. Raman spectroscopy was used to show the state of graphene oxide and further demonstrated that PPy and rGO had existed of on the foam Ni matrix. The data of EIS also suggested the charge transfer of the new composite electrode decreased compared to Pd/PPy/foam-Ni and PPy/foam-Ni composite electrodes. The effect of the electropolymerization potential on Pd/PPy-rGO/foam-Ni electrode for removing triclosan (TCS) was examined. It was found that the removal efficiency of TCS on the composite electrode could reach 100% at electropolymerization potential of 0.7 V and reaction time of 100 min.     

Relationship between the reactions of hydrogen sorption/desorption and methanol oxidation on bifunctional Ni/Pd electrode in alkaline solution

The present paper is aimed at studying the influence of the hydrogen sorption/desorption process occurring on the layered nickel–palladium (Ni/Pd) electrode on the kinetics of the reaction of methanol oxidation in strong alkaline KOH solution. The electrodes were prepared by chemical deposition of a thin layer of porous palladium on a nickel foam support. A scanning electron microscope was used for studying the morphology of both the nickel support and the porous palladium layer. The mechanism of the anodic desorption of hydrogen changes depending on whether or not 6 M KOH electrolyte is admixed with methanol. It was shown that, in the first cycle of the cyclic voltammetry (CV) measurements, the anodic peak current and peak charge related to the oxidative desorption of hydrogen significantly decrease due to the presence of methanol in KOH. This effect is attributed to the obstacles in hydrogen sorption due to the formation of a passivating layer on the Pd surface composed of both adsorbed methanol molecules and the intermediate products involving adsorbed CO. On the other hand, hydrogen desorbing from Pd electrode exerts influence on the kinetics of the reaction of methanol oxidation. Ni/Pd electrode undergoes considerable reactivation due to the potentiostatic saturation with hydrogen at ?1.1 V, followed by the ease in hydrogen desorption. The CV measurements proved that, after such a treatment, the peak of hydrogen desorption partially overlaps the double peak of methanol oxidation and, in consequence, the rate of methanol oxidation is enhanced. The positive effect of hydrogen releasing from the electrode on the kinetics of the reaction of methanol oxidation is ascribed to the anti-poison behavior consisting in the reaction of hydrogen radicals with intermediates adsorbed on the Pd surface.     

Preparation of palladium nanoparticles–titanium electrodes as a new anode for direct methanol fuel cells

Pd nanoparticle/Ti electrodes are prepared by electroless plating of palladium on titanium plates. The morphology and surface analysis of Pd nanoparticle/Ti electrodes are investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The results indicate that palladium nanoparticles are homogeneously deposited on the surface of titanium plates. The electro-catalytic activity of Pd nanoparticle/Ti electrodes in the methanol electro-oxidation is studied by cyclic voltammetry and chronoamperometry methods. The results show that the electro-catalytic oxidation of methanol on the Pd nanoparticle/Ti electrode improved compare to pure palladium electrode and confirmed the better electro-catalytic activity and stability of these new electrodes.     

Pd/Pt二元合金电极的制备及氧还原性能

本文利用欠电位沉积亚单层的Cu及Pt置换取代Cu的方法, 制备了具有不同表面元素组成的Pd/Pt二元合金电极(用Pd/Ptx表示, x指欠电位沉积Cu-Pt置换取代Cu过程的次数),并对其表面元素组成、氧还原性能进行了表征. 在控制欠电位沉积Cu的下限电位恒定(0.34 V)的前提下, 表面Pt/Pd的元素组成比通过重复欠电位沉积Cu及Pt置换取代Cu的次数(1~5次)来可控地调变. 光电子能谱(XPS) 以及红外光谱实验表明,Pd/Ptx电极表层区的Pt：Pd元素组成比随着Pt沉积次数增加而增加, 对Pd/Pt4电极, 在电极表层区约2~3 nm内的Pt/Pd的原子比大约是1:4,而最表层裸露Pd原子的比例仍在20%以上。循环伏安结果显示, 随着Pt沉积次数的增加(1-5次), Pd/Ptx电极表面越不易被氧化。氧还原测试结果显示随着Pt沉积次数的增加(1~4次), Pd/Ptx二元金属电极的氧还原活性依次增加, 经过第3次沉积后其氧还原活性已优于纯Pt,而经4次以上沉积,其氧还原活性基本不变。在其它反应条件相同条件的前提下, Pd/Pt4电极上氧还原的半波电位与纯Pt相比右移约25 mV。结合本文与文献的实验结果,我们初步认为Pd/Ptx二元金属体系氧还原性能改善主要源自表层Pd原子导致其邻近的Pt原子上含氧物种吸附能的降低.     

纳米钯催化剂对甲醇的电催化氧化

采用水热法,以甲醛作还原剂还原Pd2+-EDTA络合物,制得钛基纳米钯颗粒电极(nanoPd/Ti).扫描电子显微镜(SEM)显示,纳米钯颗粒直径约为60 nm,形成三维立体网状结构.在碱性溶液中,循环伏安及交流阻抗测试分别表明:nanoPd/Ti电极对甲醇氧化有极高的阳极电流、较低的起始氧化电位和较强的抗CO毒化能力.在nanoPd/Ti电极上甲醇电氧化反应的阻抗值较低,增加甲醇浓度,电极阻抗更低.电极对甲醇氧化具有极好的电催化活性.     

Ethanol electrooxidation on Pd/C nanoparticles in alkaline media

Carbon-supported Pd nanoparticles were prepared by microwave heating-glycol reduction method, and characterized by a wide array of experimental techniques including X-ray diffraction spectroscopy(XRD) and transmission electron microscopy(TEM). The electrooxidation behaviors of ethanol on the Pd/C electrode in alkaline media were investigated using cyclic voltammetry(CV), chronoamperometry(CA), electrochemical impedance spectroscopy(EIS) and single cell performance methods. Pd/C electrode for ethanol oxidation showed high electro-catalytic activity and long term stability. However, it is observed that the current density decreases with the increasing of the potential and negative impedance presents in the potential from-0.1 to0.1 V. The decreasing current density and the negative impedance could be due to the adsorbed intermediates species that inhibited the further oxidation of ethanol. Based on the chemical reaction analysis and EIS spectra, equivalent circuits relating to various potential zones have been obtained. These results reveal the dynamic adsorption of intermediates species on Pd surfaces. Significantly, it is clarified that the adsorption behavior begins from the maximum catalysis of electro-catalysis and ends in the formation of the palladium(II) oxide layer on the electrode surface.     

纳米钯膜电极的制备、结构表征和特殊反应性能

用循环伏安方法制备纳米钯膜电极,运用扫描隧道显微镜和原位红外光谱等方法研究其结构和反应性能.STM图像表明,制备的纳米钯膜具有特殊的层状结构,纳米级厚度的层状晶体由直径6nm左右的Pd微晶聚集而成.发现当钯膜厚度为几个纳米时,CO的吸附表现出异常红外效应,即红外谱峰反向和红外吸收显著增强(增强因子可达42.6).纳米钯膜电极对氢的反应也具有特殊的性能,与氢向钯晶格扩散吸收过程相比较,氢吸脱附的表面过程成为主要反应.研究结果还指出,纳米钯膜电极的异常红外效应和对氢反应的特殊性能与钯膜厚度密切关联,并可归结为钯膜材料的纳米尺度效应.     

Characteristics of Pd/Nafion oxygen sensor modified with polypyrrole by chemical vapor deposition

In this study, Pd/Nafion electrodes were prepared by impregnation-reduction methods in sensing oxygen. To prolong the electrode's life in practical use, a polypyrrole (PPy) film was chemically deposited onto the Pd/Nafion electrode. The sensitivities of PPy-modified Pd/Nafion electrodes are 0.00671 and 0.0117 μA/ppm obtained in O₂ concentration regions of 0–5000 and 5000–50,000 ppm, respectively. Generally, the response time and the recovery time decreases and increases significantly with increasing O₂ concentrations. After continuous aging tests for 48 h, the sensitivities of the Pd/Nafion and the PPy-modified Pd/Nafion electrodes decrease by 97% and 53%, respectively. Electronic Publication     

Thermal behavior of polarized Pd/D electrodes prepared by co-deposition

Thermal behavior of polarized Pd/D electrode, prepared by the co-deposition technique, serving as a cathode in the Dewar-type electrochemical cell/calorimeter is examined. It is shown that: (i) excess enthalpy is generated during and after the completion of the co-deposition process; (ii) rates of excess enthalpy generation are somewhat higher than when Pd wires or other forms of Pd electrodes are used; (iii) positive feedback and heat-after-death effects were observed; and (iv) rates of excess power generation were found to increase with an increase in both cell current and cell temperature, the latter being higher.     

Formation and electrocatalytic properties of Pd deposits on Mo obtained by galvanic displacement

A Pd-Mo electrocatalytic system was obtained by forming palladium particles on the Mo surface that contacted a PdCl₂ solution under open-circuit conditions. The state of palladium on the electrode surface depended on the contact displacement time. Palladium particles 5–10 nm in size formed on the surface of the Pd(Mo) electrode after palladium deposition for 1 min. The specific rates of formic acid oxidation on the Pd(Mo) electrode were smaller than those on the Pd/Pt electrode. On the Pd(Mo) electrode, anode currents of methanol oxidation were recorded at a potential of 0.4 V. The difference in the effects of the Mo substrate on the activity of Pd particles in the electrooxidations of HCOOH and CH₃OH was explained by the difference in the mechanisms of these reactions.     

The Character of Photo-electrochemistry of Palladium Implanted TiO_2 Nano-crystalline Electrode

Many methods have been adopted to improve the character of photo-electrochemistry of TiO21,2. Ion implantation is a technique with unique advantage to modify other electrodes and has been used in many electrochemical research fields3. In this paper we chose palladium ion implantation to modify nano-crystallineTiO2 and investigated the effect of implanted Pd. ExperimentalThe nano-crystalline TiO2 was prepared with hydrothermal method which was reported elsewhere4. The pH of reaction media w…     

镀Pd的GC电极上HCOOH的电催化氧化

在玻璃碳 (GC)基底上电沉积Pd ,应用SEM观测Pd沉积层的表面形貌 ,用循环伏安法研究了Pd/GC电极上HCOOH在HClO4溶液中的电氧化行为 .结果表明 ,Pd的电沉积条件影响电极的催化性能 .在高电流密度下制得的Pd/GC电极对HCOOH的电氧化具有比纯Pd电极更高的催化活性 .当电极表面生成PdO时 ,HCOOH被电氧化的活性很低 ,而在PdO还原后生成的Pd表面 ,HCOOH的电氧化显示极高的活性 .本文还讨论了Pd(Ⅱ )离子对HCOOH电氧化过程的影响 .     

Pd/Mm(富铈稀土)薄膜电极在KOH溶液中的电化学行为

利用磁控溅射法制备了Pd/Mm(Mischmetal)混合稀土薄膜,采用X射线衍射、AFM及循环伏安和交流阻抗谱等电化学测试技术研究了Pd/Mm稀土薄膜的晶体结构、表面形貌及其在KOH溶液中的电化学行为.结果表明,Pd/Mm薄膜表面的Pd层由纳米级的孤岛状颗粒构成,颗粒大小为100～200 nm.循环伏安法研究表明,氢的电化学氧化和还原均通过表面Pd金属层进行.Pd/Mm稀土薄膜电极的交流阻抗图由两个容抗弧组成,低频区的容抗弧对应氢在电极中的固态扩散过程,而高频段的容抗弧对应氢在电极表面的电化学还原过程,其中氢在薄膜电极内部的扩散是速率控制步骤.     

Synthesis of a Water Dispersion of the PEDOT:PSS/Pd Composite and Its Use for the Fabrication of an Electrochemical Sensor for Hydrazine

Conditions are studied for the synthesis of water dispersions of polymer composites containing palladium and the possibility of their use for the fabrication of modified electrodes is estimated. Water dispersions of the polymer poly(3,4-ethylenedioxythiophene), including a polystyrene sulfate polyanion (PEDOT:PSS) and Pd particles, were obtained by the redox reaction of Pd(II) with the polymer. The electrochemical behavior of composite PEDOT:PSS/Pd films in the medium of a phosphate buffer solution with pH 6.86 is studied. It is shown that, in the presence of hydrazine in a phosphate buffer solution, one wave of hydrazine oxidation on metal inclusions, Pd particles, is observed on the electrode. Specific features of the process of hydrazine oxidation are studied and a possibility using the obtained material for the creation of an electrochemical sensor for hydrazine is demonstrated.     

无配体Pd/LDH-F催化剂在Heck和Suzuki反应中的应用

 以氟离子插层的水滑石LDH-F为载体,用逐滴浸渍法制备了新型Pd/LDH-F催化剂,并用其催化溴代芳烃的Heck和Suzuki偶联反应. 用X射线衍射表征了催化剂的晶相,以等离子体发射光谱测定了溶剂中钯的流失量. 结果表明,对于Heck反应,在无配体存在和低钯用量(Pd/溴代芳烃摩尔比为0.001)的情况下, Pd/LDH-F的催化性能优于其它载体负载的Pd催化剂,显示出很高的催化活性和选择性. 在140 ℃和12 h的条件下, Pd/LDH-F催化溴苯与苯乙烯Heck反应产物的收率可达86％, 反应后催化剂经过分离,可循环使用四次其催化活性基本不变. 在DMF/水摩尔比为0.5的混合溶剂中,在室温和3 h 的条件下, Pd/LDH-F (Pd/溴代芳烃摩尔比为0.005)催化溴苯与苯基硼酸盐的Suzuki反应中,目标产物收率为99%.     

Sonochemical Synthesis of Three-dimensional Aggregates of Pd Nanoparticles with High Electrocatalytic Activity Towards Ethanol Oxidation

Flower-like aggregates composed of （4.0±0.8） nm palladium（Pd） nanoparticles were prepared via ultrasonics in the palladium（Ⅱ） chloride（PdCl2） H2O/EtOH（5/1,volume ratio） solution with the addition of a quantity of poly（vinyl pyrrolidone）（PVP） and sodium dodecyl sulfonate（SDS）.The morphologies,crystal structures and the optical properties of the flower-like Pd nanostructures were characterized by X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,selected area electron diffraction（SAED） and UV-visible absorption spectroscopy,respectively.The mechanism of sonochemical reduction of Pd（Ⅱ） ions was also investigated.The results show that the molar ratio of PVP to SDS affected the formation of the flower-like aggregates of Pd nanoparticles.Moreover,the electrocatalytic properties of Pd aggregates modified glassy carbon electrode for ethanol oxidation were also investigated by cyclic voltammetry（CV）.This material exhibits remarkable electrocatalytic activity for ethanol oxidation in 1 mol/L KOH and appears as a promising candidate to be applied in direct ethanol fuel cells.     

Biodeposited Pd/Au bimetallic nanoparticles as novel Suzuki catalysts

The use of two nanoparticulate palladium based catalysts in the Suzuki reaction is described. One monometallic (Pd) and one bimetallic (Pd/Au) catalyst were prepared by the environmentally benign method of bioreductive precipitation by Shewanella oneidensis. Both catalysts successfully mediated the Suzuki coupling, however, the Au doped catalyst was shown to deliver more reproducible results with a broader reaction scope.     

Bismuth modified Pd/C as catalysts for hydrogen related reactions

The electrocatalytic activity of bimetallic BiPd catalysts supported on Sibunit carbon towards hydrogen oxidation/evolution reactions (HOR/HER) was studied in a gas diffusion electrode (GDE) setup. Catalysts were synthesized by deposition of Pd on the carbon support, followed by impregnation of Pd/C precursor with Bi(NO₃)₃ solution and reduction in hydrogen. Transmission electron microscopy and local EDX elemental analysis revealed that BiPd/C catalysts contain bimetallic particles with narrow size distribution with maxima at 3.2–4.1 nm. X-ray diffraction evidenced that bimetallic particles are constituted by Pd–Bi solid solution. It was shown that modification of Pd/C by bismuth increases the specific activity of palladium towards HOR/HER by a factor of 3.     

Pd/Al2O3催化剂催化毛竹与聚乙烯共裂解反应研究

我们采用等体积浸渍法制备了Al2O3负载贵金属Pd系列催化剂,分别在N2和H2气氛下,研究了不同Pd负载量的催化剂对毛竹和低密度聚乙烯(LDPE)混合物的催化裂解性能.实验结果表明:Pd的负载量为1.0%时,Pd/Al2O3催化剂在两种气氛下活性均较好,在H2气氛下所得到的油品中烯烃含量较低,异链烷烃和环烷烃含量较高,油品的收率和质量均明显优于在N2气氛下所得到的油品.XRD表征发现,Pd负载量为1.0%的催化剂上,Pd在Al2O3载体上生成了晶形,表明金属钯有利于毛竹和LDPE共裂解生成液体产物.     

Simple preparation and catalytic activity of Pd particles dispersed mesoporous carbons from poly(VDC/MA) containing Pd and Y compounds

We report a simple preparation of Pd particles dispersed mesoporous carbons. The carbons were prepared by steam activation of carbonized vinylidene chloride/methyl acrylate copolymer (poly(VDC/MA)) containing yttrium acetylacetonate (Y(acac)(3)) and palladium acetylacetonate (Pd(acac)(2)). The resulting carbons consist of high contents of mesopore and uniformly dispersed fine Pd particles. We measured the catalytic activities of the carbons obtained for hydrogenation of methyl linoleate. The Pd particles dispersed in mesoporous activated carbons obtained from poly(VDC/MA) containing both Y(acac)(3) and Pd(acac)(2) showed high catalytic activities, compared with the microporous activated carbon obtained from poly(VDC/MA) containing only Pd(acac)(2). Especially Pd particles dispersed in mesoporous carbons exhibited excellent selectivity for hydrogenation of diene (methyl linoleate) to monoene (methyl oleate).