Electrochemical properties of stoichiometric RuN film prepared by rf-magnetron sputtering: A preliminary study

The electrochemical properties and stability of ruthenium mononitride (RuN) thin films were studied. Coatings of RuN were synthesized on electropolished titanium supports by rf-magnetron sputtering. RuN electrodes appear rather stable against dissolution, independently of pH, but show to possess the greatest stability only in alkaline environment. Under hydrogen evolution conditions the films show relevant catalytic properties, comparable with Pt, Pd and Ru/Ir derivatives; a significant coverage by adsorbed reaction intermediates is involved. These electrodes are of potential application in energetics and sensoring.     

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.     

Catalytic Dechlorination of Chlorobenzene in Water by Pd／Fe System

Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min^-1.     

The roughened silver–palladium cathode for electrocatalytic reductive dechlorination of 2,4-Dichlorophenoxyacetic acid

The roughened silver–palladium (Pd/Ag(r)) electrode was fabricated by a convenient metallic replacement reaction, and its electrocatalytic property towards reductive dechlorination of 2,4-Dichlorophenoxyacetic acid (2,4-D) in basic aqueous solution have been evaluated. Experimental evidence is presented that Pd/Ag(r) exhibited powerful electrocatalytic activity for dechlorination of 2,4-D. In addition, a new dechlorination mechanism of 2,4-D was proposed, in which the formation of adsorbed 2,4-D on Ag is a key step.     

电化学去合金化Pt(Pd)-Cu对氧的电催化还原活性的研究

应用电化学去合金法制备了表面覆盖有Pt(Pd)原子层的Pt(Pd)-Cu合金催化剂.研究该催化剂在0.1mol.L-1HClO4酸性溶液中对氧气电化学还原的催化活性,并采用同步辐射反常X-射线衍射法(Anomalous X-ray Diffraction,AXRD)和表面X-射线散射法(Surface X-ray Scattering,SXS)从原子尺度研究了去合金化后催化剂的结构.分析对比纳米颗粒、薄膜和单晶3种不同形式的去合金化Pt-Cu的结构和催化活性以及Pt-Cu和Pd-Cu两种不同合金薄膜的结构和催化活性.结果表明,表面应力是影响催化剂催化活性的关键因素,而应力大小则与去合金化后所形成的表面Pt(Pd)层的厚度相关,材料尺寸和组成元素等都影响表面Pt(Pd)层的厚度.提出可利用调控材料表面的应力来设计高催化活性的催化剂.     

Fabrication of monometallic (Co,Pd, Pt,Au) and bimetallic (Pt/Au,Au/Pt) thin films with hierarchical architectures as electrocatalysts

Co thin films with novel hierarchical structures were controllably fabricated by simple electrochemical deposition in the absence of hard and soft templates, which were used as sacrificial templates to further prepare noble metal (Pd, Pt, Au) hierarchical micro/nanostructures via metal exchange reactions. SEM characterization demonstrated that the resulting noble metal thin films displayed hierarchical architectures. The as-prepared noble metal thin films could be directly used as the anode catalysts for the electro-oxidation of formic acid. Moreover, bimetallic catalysts (Pt/Au, Au/Pt) fabricated based on the monometallic Au, Pt micro/nanostructures exhibited the higher catalytic activity compared to the previous monometallic catalysts.     

电化学沉积技术制备LiNiO2薄膜及表征

Well-crystallized LiNiO₂ thin films were prepared directly on nickel substrates in LiOH solution by constant current electrochemical deposition technique at 95 ℃. The as-prepared LiNiO₂ thin films were characterized by using XRD, SEM and XPS, and the results reveal that the as-prepared LiNiO₂ thin films are dense and uniform in surface and show hexagonal structure. The influence of processing parameters such as reaction temperature, duration, electrical current density as well as the concentration of LiOH solution on the structure and morphologies of as-prepared LiNiO₂ thin films were studied，and the preferable electrochemical processing conditions for preparing LiNiO₂ thin films were suggested.     

Electropolymerization of Pd(II) complexes containing phosphinoterthiophene ligands

A series of Pd complexes of 3'-diphenylphosphino-2,2':5'2' '-terthiophene (1a, dppterth) in which the metal is coordinated in three different modes have been prepared and electropolymerized, resulting in the formation of conductive thin films. In [Pd2(mu-Cl2)(dppterth-P,C3)2] (3a) the metal is P,C-coordinated, in [PdCl2(dppterth-P)2] (4a) the coordination is monodentate via the phosphine, and in [Pd(dppterth-P,C3)(dppterth-P,S1)][PF6] (5a) both P,C- and P,S-coordination modes are found. In 5a, the coordinated thiophene is hemilabile and may be displaced by reaction with more strongly coordinating ligands such as isocyanides. To probe the effect of blocking the alpha-position of the terthienyl moiety with methyl groups, 3'-diphenylphosphino-5-methyl-2,2':5'2' '-terthiophene (1b, Me-dppterth) and 3'-diphenylphosphino-5,5' '-dimethyl-2,2':5'2' '-terthiophene (1c, Me2-dppterth) were prepared, and the corresponding series of Pd complexes was synthesized. One of these complexes, [Pd(Me2-dppterth-P,C3)(Me2-dppterth-P,S1)][PF6] (5c), has been crystallographically characterized. The electropolymerized films prepared from 5a react with isonitriles, and shifts in the absorption spectra of the electropolymerized materials are observed upon reaction. A Pd complex has also been prepared from 5-diphenylphosphino-2,2':5'2' '-terthiophene (2, 5dppterth), and this complex has been electropolymerized. All the electropolymerized thin films have been characterized using EDX analysis, which demonstrates good correspondence with the elemental analysis of the respective monomers, and the maximum conductivities of the films are near 10(-4) S x cm(-1). Comparing the electropolymerization behavior of the complexes, along with their electrochemical and spectroscopic data, allows conclusions to be drawn regarding the involvement of pi-delocalization and the metal group in the conductivity of the materials.     

Hydrogen absorption by a palladium electrode from a protic ionic liquid at temperatures exceeding 100 °C

Hydrogen adsorption in a palladium electrode driven by the electrochemical reduction of protons from a protic ionic liquid is presented. The amounts of hydrogen absorbed and desorbed in thin Pd films is similar in both the diethylmethylammonium-trifluoromethanesulfonate ionic liquid and in an aqueous H₂SO₄ solution, reaching H/Pd atomic ratios of 0.7 to 0.8. The electrochemical quartz crystal microbalance technique showed decreased absorption and desorption rates due to the slower proton transfer between the protic ionic liquid and the electrode. The use of this thermally stable ionic liquid allowed absorbing and desorbing hydrogen at temperatures up to 125 °C, increasing the rate of the reactions.     

Metalloporphyrin-Based Metal–Organic Frameworks on Flexible Carbon Paper for Electrocatalytic Nitrite Oxidation

Deposition of redox-active metal–organic frameworks (MOFs) as thin films on conductive substrates is of great importance to improve their electrochemical performance and durability. In this work, a series of metalloporphyrinic MOF crystals was successfully deposited as thin films on carbon fiber paper (CFP) substrates, which is an alternative to rigid glass substrates. The specific dimensions of the obtained films could be adjusted easily by simple cutting. Metalloporphyrinic MOFs on CFP with different active metal species have been employed for electrochemical conversion of the carcinogenic nitrite into the less toxic nitrate. The MOFs on CFP exhibit remarkable improvement in terms of the electrocatalytic performance and reusability compared with the electrodes prepared from MOF powder. The contribution from metal species of the porphyrin units and reaction mechanisms was elucidated based on the findings from X-ray photoelectron spectroscopy (XPS) and in situ X-ray absorption near edge structure (XANES) measured during the electrochemical reaction. By integrating the redox-active property of metalloporphyrinic MOFs and high conductivity of CFP, MOF thin films on CFP provided a significant improvement of electrocatalytic performance to detoxify the carcinogenic nitrite with good stability.     

Electrochemical reductive dechlorination of trichloroacetic acid on porous Ag-Pd thin foam

Porous Ag-Pd thin foam (PAPTF) possesses high electrocatalytic activities towards reductive dechlorination of trichloroacetic acid in alkaline media and is expected to be promising electro catalyst for the dechlorination of chlorinated organic wastes. The electrocatalytic activities of PAPTF depend mainly on the Ag components and the morphology. However, the content of Pd(II) in the system can strongly affect the electrocatalytic performance. In this work, PAPTF was fabricated through a rapid one-step electrodeposition method within the hydrogen bubble dynamic template and characterized by SEM, EDS, and cyclic voltammetry. Morphology and composition of as-fabricated PAPTF can be modified significantly by applying different deposition conditions, such as concentration ratio of Ag(I) to Pd(II) ions in electrolytic solution and deposition time.     

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.     

Electroformation of Pd-modified Thin Film Electrocatalysts Using E-ALD Technique

Electrochemical atomic layer deposition was used to form bimetallic (BiPd, CuPd) and trimetallic (CuBiPd) thin films via surface-confined reactions. Pd thin films were characterized by cyclic voltammetry, scanning electron microscopy (SEM) and the alloy formation with preferred Au/Pd(111) orientation was confirmed by XRD. AFM revealed uniform grain distribution, with 3D islands growing on CuBiPd. EDX verified the presence of all deposited elements. Compared to other prepared catalysts, CuBiPd catalyst showed higher activity and stability towards the ethanol oxidation reaction (EOR), as confirmed by the peak current and onset potential trends, respectively: CuBiPd (1.35 mA, −0.450 V)>CuPd (0.6016 mA, −0.442 V)>BiPd (0.275 mA, −0.384 V)>Pd (0.186 mA, −0.350 V). The EOR current on CuBiPd improved by 2.5 folds relative to Pd. The results show that CuBiPd electrocatalyst is a promising material for EOR with enhanced catalytic properties for direct ethanol fuel cell     

含氮磷酸锂薄膜在空气中的稳定性

利用射频(RF)磁控溅射方法制备了含氮磷酸锂(LiPON)薄膜. 采用SEM、XRD、XPS等技术以及交流阻抗法和电位线性扫描法, 研究了空气湿度对LiPON薄膜形貌、组成和性能的影响. 结果表明, LiPON薄膜在湿度为40%的空气环境中放置24 h后, 将发生明显的水解反应, 使LiPON薄膜表面形貌变得疏松、局部突起; PH3和NH3的产生, 使薄膜中磷元素和氮元素含量减少, 而Li2CO3的生成, 则使薄膜中碳元素和氧元素含量有明显的增加. LiPON电解质薄膜形貌和组成的变化, 造成了薄膜电化学性能的严重恶化.     

Structure and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with metallic palladium inclusions

The electrochemical behavior of PEDOT/Pd composite films obtained by the chemical deposition of ultradisperse Pd particles in the poly-3,4-ethylenedioxythiophene (PEDOT) polymer matrix was studied. The structure of the films was determined by electron microscopy and energy-dispersion X-ray fluorescence analysis. The electrochemical properties of PEDOT/Pd composite films in solutions containing hydrogen peroxide was also studied. Special attention was paid to the effect of the time of the chemical deposition of palladium in the polymer structure on the electroreduction of hydrogen peroxide in phosphate buffer solutions.     

Preparation and Electrochemical Characterization of Carbonaceous Thin Layer

Current research is largely focused on the preparation of carbon complexes for eventual applications in electrochemical energy storage systems. A carbonaceous thin layer (CT) was synthesized on a fluorine‐doped tin oxide (FTO) substrate by the carbonization of glucose. The morphological image from scanning electron microscopy showed the high uniformity of CT with full coverage on the FTO substrate. The carbon content increased from 40 % in glucose to 62 % in CT by the carbonization process. Furthermore, when CT was thermally treated under a constant flow of nitrogen gas (400 °C for 9 h, CT‐9), the carbon content increased from 62 to 79 %. The proficient interaction of CT on the FTO substrate was suitable for the electrochemical characterization and application. The CT on FTO was suitable to be used as a blocking layer for the electrochemical reaction. On the other hand, the CT‐9 showed completely different electrochemical behaviors. CT‐9 showed the significantly enhanced capacitive behavior resulted from the higher porosity of CT‐9, which was electrochemically interrogated by a redox reaction of FcMeOH/FcMeOH⁺.     

Cluster chemistry: size-dependent reactivity induced by reverse spill-over

In the present work, the CO oxidation rate on size-selected Pd clusters supported on thin MgO films is investigated in pulsed molecular beam experiments. By varying the cluster coverage independent of the cluster size, we were able to change the ratio of direct and diffusion flux (reverse spill-over) of CO onto the cluster catalyst and thus probe the influence of reverse spill-over on the reaction rate for different cluster sizes (Pd(8) and Pd(30)). The experimental results show that the change in reaction rate as a function of cluster coverage is different for Pd(8) and Pd(30). In order to explain these findings, the CO flux onto the clusters is modeled utilizing the collection zone model for the given experimental conditions. The results indicate that, for small clusters (Pd(8)), the reaction probability of an impinging CO molecule is independent of whether it is supplied by diffusion or direct flux. By contrast, for larger clusters (Pd(30)) a reduced reaction probability is found for CO supplied by reverse spill-over compared to CO supplied by direct flux.     

Electrochemical characterization of gold stepped surfaces modified with Pd

Three different single crystals, Au(111), Au(332), and Au(331), were used as the substrate for palladium deposition in the underpotential deposition (UPD) regime. The Au(111) single crystal was used for control experiments to compare the behavior of the vicinal surfaces. Cyclic voltammetry in 0.1 M sulfuric acid solution, as well as electrochemical impedance spectroscopy (EIS) were used to study the hydrogen adsorption on the Pd thin films. Our results suggest that the voltammetric peaks at approximately 0.3 V versus the reversible hydrogen electrode (RHE) are related to the adsorption of hydrogen at large palladium terraces, and that at least two adjacent Pd rows are needed in order for the adsorption to take place. Further cycling to more positive potentials leads to the oxidation and slow dissolution of the Pd film. The behavior of the oxidation cycles is explained in terms of a higher stability of Pd at the steps.     

AlN-Fe纳米复合薄膜:一种新型锂离子电池负极材料

采用脉冲激光沉积技术(PLD)制备了不同比例的Al N-Fe纳米复合薄膜(Al N和Fe摩尔比为3:1;2:1;1:1;1:2),首次研究了其作为锂离子电池负极材料的电化学行为。发现当Al N和Fe的比例为2:1时,复合薄膜具有最佳的电化学性能。在500 m A·g~(-1)电流密度下,Al N-Fe(2:1)经过100次循环充放电后容量仍能保持510 m Ah·g~(-1)。对其电化学反应机理研究发现,在放电过程中,Al N-Fe纳米复合薄膜中的Al N发生分解,Al N-Fe生成Li Al合金和Li_3N。纳米Fe颗粒的引入有效提高Al N的电化学活性;在充电过程中,部分Li_3N与Fe纳米颗粒反应生成了Fe_3N,其余部分Li_3N重新生成Al N。随后的充放电过程由Fe_3N、Al N和Al三者与Li的可逆反应共同参与,保证了Al N-Fe纳米复合薄膜优异的电化学性能。该研究为设计开发新型锂离子电池电极材料提供了一种新的思路。     

Electrochemical formation and properties of two-component films of transition metal complexes and C60 or C70

The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes, C₆₀ or C₇₀, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes, yields of formation of films containing C₇₀ are higher than yields of electrodeposition of their C₆₀ analogs. C₇₀ /M films also exhibit higher porosity in comparison to C₆₀/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical responses of these films in acetonitrile containing supporting electrolyte only. C₇₀/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C₆₀/Pd and C₇₀/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte. The C₇₀/Pd film exhibits much better capacitance performance comparison to C₆₀/Pd polymer.