Palladium Nanocomposites Research Articles

Ionic Liquid Aided Chemical Synthesis of Noble Metal Nanocomposites as Efficient Nanoelectrocatalysts

Platinum, Palladium and Gold nanocomposite using non-functionalized Multiwalled Carbon Nanotube (MWCNTs) has been prepared in the presence of phosphonium-based ionic liquid (Trihexyl Tetradecyl-phosphonium bis (trifluoromethylsulfonyl) amide) TTP(TFMS)2A. In this research, the presence of ascorbic acid (AA) in the quaternary phosphonium ionic liquid and MWCNTs without any modification, different noble metal nanocomposites of Pt, Pd and Au are formed. The mixture of MWCNT and IL has already been well-ultrasonicated until the best possible long-term stable dispersion to be formed. Under the similar time durations and similar concentrations of IL, the synthesis has been carefully performed. Working in these conditions leads to platinum-ionic liquid-MWNTs nanocomposite as black viscose powders. The nanostructures of the as-prepared nanopowders was checked with SEM. Using palladium nanocomposites as the modification agent on the glassy carbon electrode (GCE), the electrocatalytic effect of nanocomposites has been electrochemically investigated. Comparing three nanocomposites show that noble metal nanoparticles well supported on the bundles of MWCNTs but palladium NPs particle density is more than platinum NPs and PtNPs particle density is more than gold one. Anyway, the electrocatalytic activity of nanocomposites changes as PdNPs>PtNPs>AuNPs.

Formation and electroanalytical performance of polyaniline–palladium nanocomposites obtained via Layer-by-Layer adsorption and electroless metal deposition

The Layer-by-Layer (LbL) adsorption technique is used to produce thin composite layers consisting of polyaniline (PANI) and Pd particles in two different ways: (i) multistep adsorption of PANI and pre-synthesized Pd nanoparticles (NPs) and (ii) multistep adsorption of PANI and polysterene sulfonate (PSS) followed by electroless deposition of palladium particles (Pdeless). The formation of both types of composite layers is characterized by electrochemical and microgravimetric measurements.Electrochemical measurements for hydrogen peroxide reduction are carried out at neutral pH under voltammetric and amperometric conditions. It is established that the PANI–Pd NPs composites show a sensitive voltammetric response for H2O2 reduction in the 40–300μM concentration range whereas the (PANI–PSS)Pdeless composites have high intrinsic electroactivity that masks the H2O2 reductive response. The amperometric data show high sensitivity for both types of composites: PANI–Pd NPs and (PANI–PSS)Pdeless (with Pd incorporated in several electroless deposition steps). For the PANI–Pd NPs material the concentration range of linear response is 10–700μM and the limit of detection 2.6μM. The obtained non-enzymatic electrocatalytic materials are suitable for monitoring the levels of H2O2 in drinking and waste waters.

Synthesis of Poly(3,4-ethylenedioxythiophene)–Palladium Nanocomposite-coated Polymer Particles by Chemical Oxidative Seeded Dispersion Polymerization

Abstract Poly(3,4-ethylenedioxythiophene)–palladium nanocomposite was deposited in situ from water-based solution onto micrometer-sized polystyrene particles. The resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, and chemical compositions.

One-step Synthesis of Conducting Polymer–Palladium Nanocomposite Fibers by Aqueous Chemical Oxidative Polymerization

Abstract Aqueous chemical oxidative polymerization of pyrrole using PdCl2 oxidant was conducted in the presence of cetyltrimethylammonium bromide in order to synthesize polypyrrole–palladium (PPy–Pd) nanocomposite in one step. Interestingly, the PPy–Pd nanocomposite was synthesized with fibrous morphology. Transmission electron microscopy studies confirmed that Pd and PPy components formed composite in nanometer dimensions.

Surface Modification Using Prussian Blue–Gold (I)–Palladium Nanocomposite: Towards Bioelectrocatalytic Probing of Hydrogen Peroxide

The synthesis of functional Prussian blue–gold(I) suspension is reported which allow the formation of Prussian blue–gold(I)/gold–palladium nanocomposite on the addition of gold nanoparticles (AuNPs) and nanostructured palladium under ambient conditions. The first step involves the synthesis of PB–Au(I) suspension following facile chemical method by the addition of an aqueous solution of tetrachloroauric acid (HAuCl4) to an aqueous solution of potassium ferricyanide followed by ultrasonication. The suspension of PB–Au(I) after drying is converted into a blue-colored nanocomposite powder showing efficient bioelectrocatalysis. The presence of Au(I) is proved from X-ray photon spectroscopy. The PB–Au(I) suspension undergo nanocomposite formation with gold and palladium nanoparticles. Such nanocomposites are formed by allowing ultrasonication of gold nanoparticles (AuNPs) or palladium that ultimately lead to the formation of three different electrocatalytic material designated as: (1) PB–Au(I), (2) PB–Au(I).AuNPs, and (3) PB–Au(I)/AuNPs–Pd and used for the development of efficient hydrogen peroxide sensors based on graphite paste-modified electrodes. Three different systems of modified electrodes namely PB–Au(I), PB–Au(I)/AuNPs, and PB–Au(I)/AuNPs–Pd are made by mixing the composite materials, graphite powder, binder in absence and the presence of horseradish peroxidise. The performance of these modified electrodes based on electrochemical measurement suggests gradual improvement in electrocatalysis in order of PB–Au(I)/AuNPs–Pd > PB–Au(I)/AuNPs > PB–Au(I) > PB. The results of cyclic voltammery and amperometric measurements are reported in this communication. The sensitivity for H2O2 determination is found to be order of 617.3 μAmM−1 cm−2 with a detection limit of 0.1 μM for PB–Au(I)/AuNPs–Pd-modified electrode. The stability of the modified electrodes is found to be more than 3 months.

Syntheses and characterizations of multiwalled carbon nanotubes-supported palladium nanocomposites

Abstract

Bacteria Cellulose Nanofibers Supported Palladium(0) Nanocomposite and Its Catalysis Evaluation in Heck Reaction

Bacteria cellulose (BC) nanofibers supported palladium(0) nanocomposites were prepared and fully characterized in terms of morphology, crystallinity, composition, and thermal stability. The as-prepared catalyst was further successfully explored in Heck coupling reaction between aryl halide and styrene or acrylates, with a yield over 86–96% for the first coupling reaction. With coupling yields decreased less than 10% for the fifth reaction cycle, Pd/BC catalyst exhibits great potential as recyclable catalyst for Heck coupling.

Polypyrrole–Palladium Nanocomposite Coating of Micrometer-Sized Polymer Particles Toward a Recyclable Catalyst

A range of near-monodisperse, multimicrometer-sized polymer particles has been coated with ultrathin overlayers of polypyrrole-palladium (PPy-Pd) nanocomposite by chemical oxidative polymerization of pyrrole using PdCl(2) as an oxidant in aqueous media. Good control over the targeted PPy-Pd nanocomposite loading is achieved for 5.2 μm diameter polystyrene (PS) particles, and PS particles of up to 84 μm diameter can also be efficiently coated with the PPy-Pd nanocomposite. The seed polymer particles and resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, surface/bulk chemical compositions, and conductivity. Laser diffraction studies of dilute aqueous suspensions indicate that the polymer particles disperse stably before and after nanocoating with the PPy-Pd nanocomposite. The Fourier transform infrared (FT-IR) spectrum of the PS particles coated with the PPy-Pd nanocomposite overlayer is dominated by the underlying particle, since this is the major component (>96% by mass). Thermogravimetric and elemental analysis indicated that PPy-Pd nanocomposite loadings were below 6 wt %. The conductivity of pressed pellets prepared with the nanocomposite-coated particles increased with a decrease of particle diameter because of higher PPy-Pd nanocomposite loading. "Flattened ball" morphologies were observed by scanning/transmission electron microscopy after extraction of the PS component from the composite particles, which confirmed a PS core and a PPy-Pd nanocomposite shell morphology. X-ray diffraction confirmed the production of elemental Pd and X-ray photoelectron spectroscopy studies indicated the existence of elemental Pd on the surface of the composite particles. Transmission electron microscopy confirmed that nanometer-sized Pd particles were distributed in the shell. Near-monodisperse poly(methyl methacrylate) particles with diameters ranging between 10 and 19 μm have been also successfully coated with PPy-Pd nanocomposite, and stable aqueous dispersions were obtained. The nanocomposite particles functioned as an efficient catalyst for the aerobic oxidative homocoupling reaction of 4-carboxyphenylboronic acid in aqueous media for the formation of carbon-carbon bonds. The composite particles sediment in a short time (<several tens of minutes) by gravity alone and hence recycling of this catalyst is easy.

Polypyrrole–Palladium Nanocomposite-Coated Latex Particles as a Heterogeneous Catalyst in Water

Polypyrrole–palladium nanocomposite-coated cross-linked polystyrene latex particles (PS/PPy–Pd) showed an excellent catalytic activity for Suzuki and Heck reactions in aqueous media. The PS/PPy–Pd can be recovered easily and quantitatively through the repeated uses with simple filtration and they maintain their high catalytic activities. Polypyrrole–palladium nanocomposite on cross-linked polystyrene latex micro-beads (PS/PPy–Pd particles) showed an excellent catalytic activity for Suzuki and Heck reactions in water and were reused without any loss of catalytic activity.

Hydrogen sensor based on a graphene – palladium nanocomposite

A composite material was prepared from graphene and palladium nanoparticles (PdNP) by layer-by-layer deposition on gold electrodes. The material was characterized by absorption spectroscopy, scanning electron microscopy, Raman spectroscopy and surface plasmon resonance. Cyclic voltammetry demonstrated the presence of electrocatalytic centers in the palladium decorated graphene. This material can serve as a sensor material for hydrogen at levels from 0.5 to 1% in synthetic air. Pure graphene is poorly sensitive to hydrogen, but incorporation of PdNPs increases its sensitivity by more than an order of magnitude. The effects of hydrogen, nitrogen dioxide and humidity were studied. Sensor regeneration is accelerated in humid air. The sensitivity of the nanocomposite depends on the number of bilayers of graphene–PdNPs.

Suzuki-Miyaura Coupling with Sn6O6-Pd Nanocomposites

A palladium nanocomposite, NP-1, was prepared by the reduction of PdCl2 with NaBH4 in the presence of a phosphine-rich hexa-meric organostannoxanne, PDrum, in 90% yield. Treatment of NP-1 with hexane gave another palladium nanocomposite, NP-2, in 65% yield. The NP-1-catalyzed Suzuki-Miyaura reaction of aryl halides 1a-i, including the aryl chlorides, with phenylboronic acid (2) in refluxing toluene gave the corresponding biaryls 3a-i in 67-99% yield. NP-2 promoted the cross-coupling in refluxing methanol to afford the corresponding biaryls 3a-h in 40-99% yield.

Organostannoxane-Supported Palladium Nanoparticles. Highly Efficient Catalysts for Suzuki-Coupling Reactions

A phosphine-rich hexameric organostannoxanne, [n-BuSn(O)COOL]6 (PDrum; L = p-PPh2-C6H4−), has been synthesized by a 6:6 reaction between [n-BuSn(O)OH]n and p-Ph2PC6H4COOH. 119Sn{1H} NMR of PDrum revealed a single resonance at −481.0 ppm, indicating that it possesses the characteristic drum structure that is well-known among organostannoxanes. Reduction of PdCl2 with NaBH4 in the presence of PDrum afforded a palladium nanocomposite, NP-1. HRTEM of NP-1 indicates that the average nanoparticle size is about 3 nm. The latter has been shown to be very effective in mediating Suzuki-coupling reactions involving a number of different substrates. NP-1 can be recycled, and HRTEM analysis of the used catalyst reveals some agglomeration. Treatment of NP-1 with n-hexane and cooling to −25 °C afforded another palladium nanocomposite, NP-2. The latter also is very effective in catalyzing the Suzuki-coupling reaction. HRTEM of NP-2 shows an average nanoparticle size of about 4.3 nm, which remains nearly unchanged even af...

Sonochemical synthesis of tungsten carbide–palladium nanocomposites and their electrocatalytic activity for hydrogen oxidation reaction

Nanocomposites between β-WC and Pd nanoparticles supported on carbon are synthesized and their electrocatalytic properties for the hydrogen oxidation reaction have been investigated. The Pd nanoparticles are obtained by a chemical reduction reaction of PdCl 2 and the β-WC nanoparticles by a sonochemical decomposition of W(CO) 6 on Pd-loaded carbon followed by heat-treatment. Depending on the relative amounts of W to Pd, the Pd nanoparticles can be reacted with W to form Pd–W alloy nanoparticles. The Pd–W alloy, whose composition is estimated to have W less than 18 at.% based on its lattice parameter, lost most of the catalytic activity of Pd. On the other hand, the nanocomposite between β-WC and pure Pd shows an enhanced activity compared with that of Pd nanoparticles alone. This enhancement can be explained with the H +-spill-over to β-WC.

Nanocomposite Hydride LaNi&lt;sub&gt;5&lt;/sub&gt;/A- and Mg&lt;sub&gt;2&lt;/sub&gt;Ni/A-Type Materials (A=C, Cu, Pd)

In this work, we have synthesized LaNi5/A and Mg2Ni/A (A = graphite, copper or palladium) nanocomposites. The A elements were distributed on the surface of ball milled alloy particles homogenously and role of these particles is to catalyze the dissociation of molecular hydrogen on the surface of studied alloy. Mechanical coating with graphite or palladium effectively reduced the degradation rate of the studied electrode materials. Results showed a significant broadening of the valence bands of studied nanocomposites compared to those obtained by theoretical band calculations. The reasons responsible for the band broadening of the nanocrystalline LaNi5- and Mg2Ni-type alloys are probably associated with a strong deformation of the nanocrystals in the mechanically alloyed (MA) samples. Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded. The valence band spectra of the MA samples could be also broadened due to an additional disorder introduced during formation of the nanocrystalline structure.

Highly efficient and reusable hydrogel-supported nano-palladium catalyst: Evaluation for Suzuki–Miyaura reaction in water

Ligand-free, palladium-supported, poly( N-isopropylacrylamide- co-potassium methacrylate) [poly(NIPA- co-PMA)] hydrogel nanocomposite with different comonomer ratios were synthesized. The developed hydrogel–palladium composites were characterized by SEM, TEM, UV–vis DRS and XRD. The catalytic performance of these hydrogel–palladium nanocomposites was examined for Suzuki–Miyaura cross-coupling reaction of aryl halides with arylboronic acids in an aqueous medium. The hydrogel with comonomer ratio of 8.8:1.6 mmol of NIPA:PMA exhibited optimum catalytic activity, which can be effectively reused 5–6 times without loss of catalytic activity.

Poly(Methyl methacrylate)/Palladium Nanocomposites: Synthesis and Characterization of the Morphological, Thermomechanical, and Thermal Properties

PMMA/Pd nanocomposites were prepared by means of free radical polymerization of methyl methacrylate using AIBN initiator in the presence of palladium acetate at 50 °C (48 h), and subsequent thermal conversion of palladium acetate into palladium metal at 120 °C (1 h). Morphological, thermomechanical, and thermal properties of PMMA/Pd nanocomposites were studied as a function of Pd content which was varied between 0.0001 and 0.01 vol%. According to transmission electron microscopy analyses of thin sections, the average Pd nanoparticle size increased slightly from 1.9 to 2.5 nm with increasing Pd content. Size exclusion chromatography revealed that MMA polymerization was not affected by the presence of Pd acetate. The elastic modulus and glass transition temperature, as determined by dynamic mechanical analysis, decreased from 3.4 GPa and 130 °C for neat PMMA to 2.85 GPa and 122 °C for PMMA/Pd containing 0.01 vol% Pd. Thermogravimetric analysis showed that the presence of small amounts of Pd (0.0005−0.005 vo...

Preparation of PAMAM− and PPI−Metal (Silver, Platinum, and Palladium) Nanocomposites and Their Catalytic Activities for Reduction of 4-Nitrophenol

Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4). The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 5.6-7.5, 1.2-1.6, and 1.6-2.0 nm, respectively. It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles. Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites. In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest.

A Novel Ultraviolet Irradiation Technique for Fabrication of Polyacrylamide–metal (M = Au, Pd) Nanocomposites at Room Temperature

Polyacrylamide (PAM)–metal (M = gold, palladium) nanocomposites with metal nanoparticles homogeneously dispersed in the polymer matrix have been prepared via a novel ultraviolet irradiation technique at room temperature, which is based on the simultaneous occurrence of photo-reduction formation of the colloidal metal particles and photo-polymerization of the acrylamide (AM) monomer. The UV–vis absorption spectra and TEM were employed to characterize the M-PAM nanocomposites by different irradiation times. The average sizes of the colloidal gold and palladium particles dispersed in the nanocomposites were calculated by XRD patterns and TEM images. The present method may be extended to prepare other metal–polymer hybrid nanocomposite materials.