Palladium electrodeposition on polyaniline films

The electrochemical nucleation and growth of palladium particles onto polyaniline (PAni) films have been investigated by chronoamperometry and topographic and phase-mode atomic force microscopy (AFM). The films were synthesized under different potentiodynamic conditions in order to obtain polymer layers with comparable electroactivity but distinctly different morphology/porosity. The analysis of the current transients obtained for the initial stages of the Pd deposition indicates a 3D nucleative formation regime. A detailed Pd electrodeposition study onto the polymer matrix, using different deposition times, suggests that a constant number of critical nuclei is formed in the superficial part of the polymer porous matrix in the time scale between ca. 5 and 15 s.     

Co-deposition mechanism of nanodiamond with electrolessly plated nickel films

The co-deposition behavior and mechanism of nanodiamond with electrolessly plated nickel films was investigated. Due to the variation of complexing agents, various composite films with 0.9-8.0% nanodiamond were plated from electroless nickel plating baths which contained the same amount of nanodiamond (5.0 g dm⁻³) and sodium hypophosphite. In addition, composite films with 0-14% nanodiamond, semi-brilliant, were successfully fabricated from the bath which contained only citrate as a complexing agent. The plating bath was very simple and was sufficiently stable without any decomposition until termination of the plating reaction occurred due to consumption of the reducing agent. When the adsorbed amount of Ni-complex on the nanodiamond particles was large, a large amount of nanodiamond was co-deposited with the nickel. The results are interpreted to indicate that the adsorbed Ni-complex precipitates the incorporation of nanodiamond particles into the nickel matrix. In addition, incorporation becomes more probable when the adsorbed amount of Ni-complex on the nanodiamond particles was large.     

Electrochemical behavior of a novel palladium pentacyanonitrosylferrate modified aluminum electrode

Novel inorganic film modified electrodes have been prepared by chemical deposition of a thin palladium pentacyanonitrosylferrate (PdPCNF) film on the surface of aluminum substrate. The modification process including the electroless deposition of metallic palladium on the aluminum electrode surface from PdCl₂+25% ammonia solution and chemical derivatization of deposited palladium to the PdPCNF film in 0.1 M Na₂[Fe(CN)₅NO]+0.5 M KNO₃+HNO₃ solution (pH 1.5-2.5), are described. The aluminum-based modified electrodes exhibit, one pair of well-defined voltammetric peaks which correspond to the Fe(III)/Fe(II) transition in complex structure. The effect of pH, ammonium, alkali metal and alkaline earth metal cations of supporting electrolyte on the electrochemical characteristics of the modified electrode was studied in detail. Diffusion coefficients of hydrated ammonium and alkali metal cations in the film (D), transfer coefficient (α) and transfer rate constant for electron (k_s), were determined. The high stability of this modified electrode makes it attractive in practical application.     

Formic acid oxidation at spontaneously deposited palladium on polyaniline modified carbon fibre paper

Extended reaction zone anodes for formic acid oxidation have been prepared by the spontaneous deposition of Pd on polyaniline coated carbon fibre paper. The PANI supports, deposited on carbon fibre paper either galvanostatically, potentiostatically, or potentiodynamically, were characterized by electron microscopy, cyclic voltammetry and impedance spectroscopy. Pd was deposited on them by spontaneous reduction of Pd(II) by the reduced form of the PANI in order to preserve the characteristics of each type of PANI layer. It was found that galvanostatically deposited PANI produced electrodes that were much more active for formic acid oxidation than PANI produced under potential control. The morphology and mean particle size of Pd was found to depend strongly on the way in which the PANI was prepared and also correlated with the resistance and capacitance of the PANI at low potentials. It is proposed that the electrochemical characteristics of the PANI play a significant role in determining the morphology, particle size, and electrocatalytic activity for formic acid oxidation of the spontaneously deposited Pd.     

Poly(o-toluidine) as the matrix for incorporation of palladium species from PdCl2 aqueous solutions

Reactivity of poly(o-toluidine) in the emeraldine base form (POT) and protonated with HCl (POT/HCl) in PdCl₂ aqueous solutions of various HCl concentrations has been studied. Using elemental analysis, FTIR, UV–Vis, XPS and EXAFS spectroscopies as well as XRD and SEM it has been established that POT/HCl is more reactive than POT. The course of reactions is influenced by the type of the PdCl₂ solution. Thus, protonation of POT with incorporation of palladium (II) chloro–and/or aquachloro–and/or chlorohydroxycomplexes counterions is the main process occurring in the PdCl₂ solutions of higher HCl concentration. A redox reaction resulting in the oxidation of the polymer chain with simultaneous formation of metallic palladium takes place in the PdCl₂ solution of lower HCl concentration. POT/HCl shows enhanced reducing properties with respect to POT. Lowering of the protonation level (i.e. some deprotonation) of POT/HCl has been also observed. Coordination of palladium (II) ions by nitrogen atoms of the polymer chain can be also postulated.     

Effect of surface roughness on the adhesion of electrolessly plated platinum to poly(ethylene terephthalate) films

Poly(ethylene terephthalate) films were treated with aqueous sodium hydroxide solutions of different concentrations for various times. The rate of weight loss increased with the addition of a swelling agent (methylene chloride) or a cationic surfactant. The surface roughness of the treated films was determined from atomic force microscopy (AFM) and pore diameter was obtained from scanning electron microscopy (SEM). In general, surface roughness was found to increase with increasing weight loss for the treated films. A maximum roughness was obtained for samples with a weight loss of approximately 15-20%, beyond which the roughness of the samples decreased. The addition of methylene chloride and surfactant resulted in an almost two-fold increase in the roughness for all treatment times investigated. The adhesion of electrolessly plated platinum film was dependent on the contact area produced by chemical treatment. Treatments producing smaller diameter pores of greater depth gave better adhesion.     

Electroless versus electrodriven deposition of silver crystals in polyaniline: Role of silver anion complexes

Electrocrystallization of silver is studied at polyaniline-coated electrodes using silver cations and two silver anion complexes (silver thiosulfate and silver–EDTA) as reducing species. Use of the silver thiosulfate complex results in a significant shift of the silver deposition potential window in the negative direction and highly impeded metal crystallization. The silver cation and silver–EDTA plating solutions allow to perform both electrodriven and electroless metal deposition. Number and size of silver crystals obtained by the two deposition methods in the different plating solutions are compared. Electroless precipitation in the silver–EDTA solution results in the highest number (10⁸ cm⁻²) of small-sized crystals. This result is discussed in terms of the special role of the EDTA anions for the redox state of the polyaniline layers. It is demonstrated that factors such as polyaniline redox charge, concentration of reducing ions and dipping time allow effective control over the amount of electroless deposited metal.     

Electroless versus electrodriven deposition of silver crystals in polyaniline: Role of silver anion complexes

Electrocrystallization of silver is studied at polyaniline-coated electrodes using silver cations and two silver anion complexes (silver thiosulfate and silver-EDTA) as reducing species. Use of the silver thiosulfate complex results in a significant shift of the silver deposition potential window in the negative direction and highly impeded metal crystallization. The silver cation and silver-EDTA plating solutions allow to perform both electrodriven and electroless metal deposition. Number and size of silver crystals obtained by the two deposition methods in the different plating solutions are compared. Electroless precipitation in the silver-EDTA solution results in the highest number (∼10⁸ cm⁻²) of small-sized crystals. This result is discussed in terms of the special role of the EDTA anions for the redox state of the polyaniline layers. It is demonstrated that factors such as polyaniline redox charge, concentration of reducing ions and dipping time allow effective control over the amount of electroless deposited metal.     

聚苯胺合成研究进展

扼要综述聚苯胺的结构、合成方法、应用现状和目前存在的问题 ,并对其今后发展趋势进行了展望。     

Aqueous pretreatments of polyetherimide to facilitate the bonding of electrolessly deposited copper

A chemical method for pretreating polyetherimide substrates to promote adhesion to copper is described. The process consists of cleaning the polymer surface followed by surface normalization, debris solubilization, and adhesion promotion via chemical modification of the polymer surface. Classes of candidates for each of the major steps are described and the optimal agents assembled into a recommended procedure. Peel strengths between 150-210 g mm^-1 for copper to polyetherimide were achieved utilizing the suggested scheme. Scanning electron microscopic and X-ray photoelectron spectroscopic analyses were employed to investigate changes in the polymer surface and chemistry during processing. Metallized specimens were examined after 90° peel testing and the failure locus found to be within the polymer layer.     

Preparation of a tubular palladium membrane by photocatalytic deposition

A novel photocatalytic deposition method for the preparation of a thin tubular palladium membrane is presented in this paper. The membrane is prepared on a porous asymmetric TiO₂ support by photocatalytic reaction of palladium ion, followed by electroless plating. Gas permeation results show that the membrane exhibits increased hydrogen permeance with the increase of temperature. The hydrogen permeance and selectivity to nitrogen at 773 K are about 1.43×l0⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ and 17, respectively, when the pressure in the feed side is 0.1 MPa. The activation energy of hydrogen permeation is 11.06 kJ/mol at the temperature range of 573–773 K.     

Polyaniline prepared in ethylene glycol or glycerol

Oxidations of aniline or aniline hydrochloride have been carried out in ethylene glycol or glycerol and in their mixtures with water. Ammonium peroxydisulfate was used as oxidant. The oxidation of aniline is exothermic and changes in temperature were monitored to follow its progress. The effect of the solvents on the course of oxidation, morphology, and properties of final products has been studied by scanning electron microscopy, FTIR spectroscopy, and conductivity measurements. It is proposed that the reduction of dielectric constant of the reaction medium results in the reduced dissociation of ionic species that take a part in oxidative polymerization. Consequently, the addition of an organic solvent has a similar effect as a decrease in the acidity of the reaction mixture. Conductivity and morphology depend on the mole ratio of oxidant and monomer, and the type and volume fractions of organic solvents, viz. ethylene glycol and glycerol, which were used in reactions.     

可溶导电聚苯胺材料的合成研究

采用乳液聚合方法，合成有机大分子酸DBSA掺杂的可溶导电聚苯胺。探讨DBSA和引发剂用量对掺杂聚苯胺电导率及其溶解性的影响。合成了电导率较高和很好溶解性的导电聚苯胺材料，可以用作抗静电材料。     

Novel visible-light-responsive photo-catalysts based on palladium decorated nanotube films fabricated on titanium substrates

A novel visible-light-responsive photo-catalyst was synthesized for the photo-degradation of methylene blue. Highly ordered and uniformly distributed titanium dioxide-tungsten trioxide nanotubes on pure titanium substrates were successfully fabricated by one-step electrochemical anodizing and palladium deposited on these nanotubes by photo-reduction method. The resulting samples were characterized by X-ray diffraction, field emission scanning electron microscope, ultraviolet–visible spectroscopy and energy dispersive X-ray spectrometer methods. The degradation of methylene blue (MB) was used as a model reaction to evaluate the photo-catalytic activity of the obtained samples. After irradiated under visible light for 60 min, degradation ratio of Pd-deposited nanotubes was improved as compared with that of bare titanium dioxide-tungsten trioxide nanotubes. Under the same condition, no obvious photo-degradation of methylene blue was found for bare TiO₂ nanotubes. Kinetic research showed that photo-degradation process followed the first-order reaction; the apparent reaction rate constant of Pd-based nanotubes was approximately 2.19 times higher than that on the unmodified nanotubes. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photo-catalytic activity.     

Electroreduction of oxygen on gold-supported nanostructured palladium films in acid solutions

The electrochemical reduction of oxygen on thin Pd films with a nominal thickness of 0.25-10 nm on polycrystalline Au substrate (Pd/Au) was studied. The Pd films were prepared by electron beam evaporation and oxygen reduction was studied in 0.1 M HClO₄ and 0.05 M H₂SO₄ solutions using the rotating disk electrode (RDE) method. The surface morphology of Pd overlayers was examined by scanning tunnelling microscopy (STM). O₂ reduction predominantly proceeds through 4e⁻ pathway on all Pd/Au electrodes. The specific activity (SA) of oxygen reduction was lower in H₂SO₄ solution and decreased slightly with decreasing the Pd film thickness. In HClO₄, the SA was higher and not significantly dependent on the film thickness. The Tafel slope values close to −60 mV at low current densities and −120 mV at high current densities were found for all electrodes.     

纳米碳管掺杂聚苯胺的光电性能

用三种方法制作了的掺杂聚苯胺,通过对材料光学、电阻、电磁参数及电磁屏蔽等特性的研究,结果表明掺杂提高了材料的电性能,但降低了其光学性能.     

导电聚苯胺复合膜的研制

以聚甲基丙烯酸甲酯(PMMA)为基质，过硫酸铵为氧化剂，十二烷基苯磺酸为掺杂剂，进行苯胺的原位氧化聚合，制备聚苯胺(PAn)／PMMA复合材料，采用溶液浇铸法制成了性能优良的可溶性导电复合膜，电导率达10^-2S／cm；考察了反应条件对复合膜电导率的影响，并进行了环境稳定性测试，用红外光谱进行了复合膜的结构表征，用元素分析法测定了复合膜的组成，结果表明复合的聚苯胺存在—饱和值，超过饱和值，对电导率影响不大。     

含氟聚苯胺的合成及性能研究

含氟的高分子聚合物,通常具有很强的抗逆性、抗高温、抗化学腐蚀、具有耐久性和耐候性,因此其在石油化学、工业建筑等方面被广泛应用,研究此类聚合物具有很强的实际意义。主要研究含氟聚苯胺,将总结它的合成方法、阐述它的性质以及实际应用。     

酸掺杂聚苯胺的研究进展

聚苯胺是最有应用价值的导电高分子之一,介绍了聚苯胺的结构,重点综述了单一无机酸掺杂、单一有机酸掺杂、复合酸掺杂、掺杂-脱掺杂-再掺杂、制备掺杂态聚苯胺的研究进展.最后,提出了聚苯胺的研究方向.