Palladium Acetylacetonate Research Articles

Size-Controlled Synthesis and Magnetic Studies of Monodisperse FePd Nanoparticles

Monodisperse FePd nanoparticles were prepared through thermal decomposition of iron carbonyl and reduction of palladium acetylacetonate in the presence of mixing capping agents. The size of FePd nanoparticles can be easily tuned from 8 nm, up to 27 nm by controlling the molar ratio of surfactants and reaction temperature. The magnetic studies indicate that the blocking temperature and coercivity of the FePd nanoparticles exhibit a size-dependent behavior.

Porous Palladium Nanoflowers that Have Enhanced Methanol Electro-Oxidation Activity

A liquid phase approach was used for the synthesis of novel porous Pd nanoflowers by the self-organization of primary nanoparticle building blocks. Palladium acetylacetonate was used as the metal precursor with 1,2-hexadecanediol as the reduction agent. The porous Pd nanostructure obtained has an average size of 50 nm and was composed of three-dimensionally connected Pd nanoparticles with an average diameter of 5.5 nm. The new Pd nanostructure has higher electrocatalytic activity and better stability for the electro-oxidation of methanol in an alkaline media than Pd nanoparticles.

Model-fitting and model-free analysis of thermal decomposition of palladium acetylacetonate [Pd(acac)2

The non-isothermal decomposition process of the powder sample of palladium acetylacetonate [Pd(acac)2] was investigated by thermogravimetric (TG) and the X-ray diffraction (XRD) techniques. Model-free isoconversional method of Tang, applied to the investigated decomposition process, yield practically constant apparent activation energy in the range of 0.05≤α≤0.95. It was established, that the Coats-Redfern (CR) method gives several statistically equivalent reaction models, but only for the phase-boundary reaction models (R2 and R3), the calculated value of the apparent activation energy (E) is nearest to the values of E obtained by the Tang’s and Kissinger’s methods.

First-principles calculations of the palladium(II) acetylacetonate crystal structure

The geometry of palladium(II) acetylacetonate in a monoclinic crystal lattice is calculated using the planewave-pseudopotential implementation of density-functional theory. Both the Troullier–Martin pseudopotential with the generalized gradient Perdew–Burke–Ernzerhof approximation and the Goedecker pseudopotential with the local density approximation are employed. The non-planar, step-like, structure of the molecule observed experimentally is successfully reproduced. A topological analysis of the electron localization function suggests a weak interaction between a Pd cation and the nearest carbon atom of the neighboring molecule of the closed-shell, non-electron-sharing type, presumably of electrostatic or dispersive nature, and possibly responsible for the bending of the palladium(II) acetylacetonate salt molecule in the crystal structure.

Synthesis and Characterization of Nanostructured Pd−Mo Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells

Carbon-supported Pd100-xMox (0 ≤ x ≤ 40) nanoparticles have been synthesized by a simultaneous thermal decomposition of palladium acetylacetonate and molybdenum carbonyl in an organic solvent (o-xylene) in the presence of Vulcan XC-72R carbon, followed by heat treatment up to 900 °C in H2 atmosphere and characterized chemically and structurally. X-ray diffraction data reveal the formation of single-phase face-centered cubic solid solutions for 0 ≤ x ≤ 30 after heat treating at 900 °C and the occurrence of a Mo2C impurity phase for x = 40. The particle size of the Pd100-xMox samples increase with increasing heat treatment temperature as revealed by transmission electron microscopy. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo enhances the catalytic activity for the oxygen reduction reaction (ORR) as well as the stability (durability) of the electrocatalyst. However, the activity reaches a maximum at Pd90Mo10 and then decreases with increasing...

Effect of Metal Salt on the Pore Structure Evolution of Pitch-Based Activated Carbon Microfibers

The effect of palladium acetylacetonate on the pore structure evolution of isotropic petroleum pitch-based activated carbon fibers (ACFs) is characterized by comparing the pore structure evolution ...

Organometallic red-emitting chromophores: a computational and experimental study on cyclometallated Nile Red complexes of palladium(ii) and platinum(ii) acetylacetonates and hexafluoroacetylacetonates

A comparative photophysical, electrochemical and computational study of a series of Nile Red cyclopalladated and newly synthesised cycloplatinated complexes is reported. All complexes are luminescent at room temperature and the emission properties are governed by the nature of the cyclometallated dye. However, the presence of platinum(II) as metal centre decreases severely the emission quantum yield, while the electronegativity of the ancillary hexafluoroacetylacetonato ligand enhanced the emission properties of the Nile Red complexes.

Palladium nanostructures synthesized by radiolysis or by photoreduction

Palladium nanostructures formed by nanowires, nanoplates or having a flower-like shape were synthesized by slow reductionviaradiolysis or via photoreduction of palladium acetylacetonate Pd(acac)2 in 2-propanol under CO atmosphere.

Doctor-bladed thick films of flame-made Pd/ZnO nanoparticles for ethanol sensing

Abstract ZnO nanoparticles doped with 0–5 mol% Pd were produced by flame spray pyrolysis (FSP) in a single step using zinc naphthenate and palladium (II) acetylacetonate as precursors dissolved in toluene/acetonitrile (80/20 vol%). The particle properties were further analyzed by XRD, BET, and HR-TEM analyses. The sensing films were produced by mixing the particles into an organic paste composed of terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed onto Al 2 O 3 substrates interdigitated with Au electrodes. The gas sensing of ethanol (25–250 ppm) was studied at 400 °C in dry air. In addition, 1 mol% Pd/ZnO film showed the highest sensitivity and fastest response times (within seconds). The sensitivity increased and the response time decreased with increasing ethanol concentration.

Effects of Palladium Loading on the Response of Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor

ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in asingle step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II)acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect ofPd loading on the ethanol gas sensing performance of the ZnO nanoparticles and thecrystalline sizes were investigated. The particle properties were analyzed by XRD, BET,AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorptionmeasurements. A trend of an increase in specific surface area of samples and a decrease inthe dBET with increasing Pd concentrations was noted. ZnO nanoparticles were observed asparticles presenting clear spheroidal, hexagonal and rod-like morphologies. The sizes ofZnO spheroidal and hexagonal particle crystallites were in the 10-20 nm range. ZnOnanorods were in the range of 10-20 nm in width and 20-50 nm in length. The size of Pdnanoparticles increased and Pd-dispersion% decreased with increasing Pd concentrations.The sensing films were produced by mixing the particles into an organic paste composedof terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed ontoAl2O3 substrates interdigitated with Au electrodes. The film morphology was analyzed bySEM and EDS analyses. The gas sensing of ethanol (25-250 ppm) was studied in dry air at400°C. The oxidation of ethanol on the sensing surface of the semiconductor wasconfirmed by MS. A well-dispersed of 1 mol%Pd/ZnO films showed the highest sensitivityand the fastest response time (within seconds).

Synthesis of colloidal particles of poly(2-vinylpyridine)-coated palladium and platinum in organic solutions under the high temperatures and high pressures

Colloidal dispersions of poly(2-vinylpyridine)-coated palladium (Pd) and platinum (Pt) particles in the toluene/1-propanol solution have been synthesized by the decomposition and reduction of palladium acetylacetonate (Pd(acac)2) and platinum acetylacetonate (Pt(acac)2) under the high-temperatures and high-pressures conditions. The size and the structure of the synthesized particles have been examined by transmission electron micrograph (TEM) and extended X-ray absorption fine structure (EXAFS). At 473 K and 25 MPa, colloidal dispersions ([Pd] = 7.5 mM) of Pd particles of 1.9 nm as an average diameter, which had narrow particle size distributions, were synthesized within a few seconds. Pt particles were also synthesized with an average diameter of 2.1 nm. On the other hand, bimetallic Pd/Pt particles were not synthesized at 473–623 K and 25 MPa, probably due to the difference of decomposition rate of each starting compound.

Graphite fluoride intercalation compounds for manufacturing composites with metal nanoparticles

The feasibility of using graphite fluoride intercalation compounds (GFICs) containing metal compounds for manufacturing metal nanoparticles in a graphite or graphite fluoride matrix is shown using the hydrogen reduction of a dicarbon fluoride matrix intercalated with a chloroform solution of palladium acetylacetonate Pd(AA)2. The composite manufactured with a GFIC containing about 10.5 wt % Pd(AA)2 at 80°C is Pd-fluorographite; at 450°C, Pd-graphite is manufactured. The palladium particle size in the composites is about 20–30 nm; the palladium concentration is about 5 and 9 wt %, respectively.

Sunflower oil hydrogenation on Pd/Al2O3 catalysts in single-phase conditions using supercritical propane

Abstract Several Pd catalysts were prepared on α and γ alumina using palladium acetylacetonate and palladium nitrate as a precursor. The characterization of these catalysts by H2 chemisorption, XRD and TEM microscopy confirm the presence of different dispersed metallic particles from 1.9 to 12.1 nm. These catalysts were tested in the sunflower oil hydrogenation under supercritical conditions using propane as solvent and 5% mol of hydrogen concentration. The well-known Weisz–Prater criterion was used to determine the extent of mass transport phenomena. While hydrogen mass transport was found free from limitations, oil transport had limitations in some experiments. The reaction is moderately structure sensitive since the turnover number decreases 3 times as the exposed metal percentage (metal dispersion) increases from 9 to 60%. An influence on the selectivities to trans isomers, monounsaturated and saturated fatty acids was found when the metallic particle size was decreased. These results are explained by the high adsorption strength of the high-unsaturated fatty acids onto the small particles and the promotion of a “shunt” reaction from linoleic to saturated compounds.

06/01165 Variability of inorganic and organic constituents in lime spray dryer ash: Taerakul, P. et al. Fuel, 2005, 84, (14–15), 1820–1829

Activated carbon fibers (ACFs) prepared from petroleum isotropic pitch and the same containing silver and cobalt nitrate, cobalt and palladium acetylacetonates, as well as mixtures of two salts with a total metal or metal mixture content of 1 wt% have been studied. The processing parameters are summarized for activated carbon fibers containing individual metals and metal mixtures. The results suggest that the generation of metal-containing particles and the formation of pore structure depend on many different factors including the composition of the metal and pitch precursors, the interaction of the metal and pitch precursors during the fiber production process, and the interaction between the two metal precursors when more than one metal salt is used. The addition of silver and cobalt in the form of nitrate salts enlarges the micropores and generates small mesopores with a narrow range of sizes. The addition of palladium as an acetylacetonate salt leads to the formation of both small micropores and larger mesopores. The cobalt additive as an acetylacetonate salt catalyzes the activation process, creating large mesopores and macropores. Mixing of two different metal precursors affects the particle composition and size. This, in turn, controls the pore structure of the final activated fibers. During activation, the two metal precursors can act independently (Ag/Co mixture). However, in other cases their effect can be additive (Co/Pd mixture), or even synergistic (Ag/Pd mixture).

Studies of the oxidation of palladium complexes by the advanced oxidation process: Pretreatment of model catalysts for precious metal analysis

The advanced oxidation process (AOP) for the pretreatment of model palladium catalysts has been studied. Most standard metal analysis techniques are for metal ions free of organic ligands. Spent palladium catalysts contain organic ligands that need to be removed prior to analysis. AOP uses a combination of hydrogen peroxide and UV light to generate radicals that decompose such ligands, freeing up metals for further analysis. Palladium acetate Pd(OAc) 2, palladium acetylacetonate Pd(acac) 2, and tris(dibenzylideneacetone)dipalladium (Pd 2(dba) 3) were chosen as model precious metal catalysts for investigation. AOP was found to decompose ligands in Pd(OAc) 2, Pd(acac) 2 and give accurate Pd(II) quantification, while ligand decomposition and oxidation of Pd(0) to Pd(II) were demonstrated in treatments involving Pd 2(dba) 3. The effects of solubility of the palladium complexes, continuous addition of H 2O 2 during AOP treatments, sample pH, concentration of H 2O 2, and length of UV irradiation are reported.

Transformation to L10 structure in FePd nanoparticles synthesized by modified polyol process

FePd nanoparticles were prepared by the modified polyol process, i.e. simultaneous reduction of palladium acetylacetonate and thermal decomposition of iron pentacarbonyl in a solvent. The well-dispersed FePd particles, with the average particle size of ~8.4 nm, were obtained using diphenyl ether as a solvent. The structure of FePd nanoparticles transformed to L10 structure from face centered cubic (fcc) structure after annealing at 600 °C for 1 h in vacuum. The coercivity of the ordered FePd nanoparticles increased to ~2 kOe at 5 K from ~0.6 kOe in the fcc as-made FePd nanoparticle. On the other hand, FePd nanoparticles, synthesized based on the conventional modified polyol process using dioctyl ether as a solvent, showed no structural transformation after annealing up to 700 °C. This is explained in terms of the interruption of thermal diffusion of Fe and Pd atoms during the thermal treatment due to the mixture of interstitial carbon impurity in the synthesis process using dioctyl ether as a solvent.

In Situ and Time-Resolved SAXS Studies of Pd Nanoparticle Formation in a Template of Block Copolymer Microdomain Structures

Time-resolved small-angle X-ray scattering (SAXS) measurements were performed to study in-situ formation of palladium (Pd) nanoparticles in block copolymer microdomains. The nanoparticles were reduced in a reaction medium containing a fixed composition of polyisoprene-block-poly(2-vinylpyridine) (PI-b-P2VP), palladium acetylacetonate, Pd(acac)2, and benzyl alcohol as a solvent and a reducing agent. The polymer concentration is high enough so that it forms swollen ordered lamellae before reduction. The reduction was induced by a rapid temperature jump, and the polymer concentration was kept constant in a sealed sample cell. It was clearly elucidated that the formation of Pd nanoparticles occurred in the templates of the swollen lamellar microdomains. By fitting the theoretical scattered intensity for spherical particles to the observed SAXS profiles, we analyzed time evolution of mean radius, standard deviation of radius, and total volume of Pd nanoparticles in concentrated PI-b-P2VP solutions after T-jump...

The application of infrared spectroscopy to probe the surface morphology of alumina-supported palladium catalysts

Five alumina-supported palladium catalysts have been prepared from a range of precursor compounds [palladium(II) nitrate, palladium(II) chloride, palladium(II) acetylacetonate, and tetraamminepalladium(II) tetraazidopalladate(II)] and at different metal loadings (1-7.3 wt %). Collectively, this series of catalysts provides a range of metal particle sizes (1.2-8.5 nm) that emphasize different morphological aspects of the palladium crystallites. The infrared spectra of chemisorbed CO applied under pulse-flow conditions reveal distinct groupings between metal crystallites dominated by low index planes and those that feature predominantly corner/edge atoms. Temperature-programmed infrared spectroscopy establishes that the linear CO band can be resolved into contributions from corner atoms and a combination of (111)(111) and (111)(100) particle edges. Propene hydrogenation has been used as a preliminary assessment of catalytic performance for the 1 wt % loaded catalysts, with the relative inactivity of the catalyst prepared from palladium(II) chloride attributed to a diminished hydrogen supply due to decoration of edge sites by chlorine originating from the preparative process. It is anticipated that refinements linking the vibrational spectrum of a probe molecule with surface structure and accessible adsorption sites for such a versatile catalytic substrate provide a platform against which structure/reactivity relationships can be usefully developed.

Methane combustion over PdO-alumina catalysts: The effect of palladium precursors

The role of palladium precursors and the preparation route in the catalytic properties of PdO/Al2O3 catalysts toward methane oxidation was investigated in this paper. The catalysts were prepared using palladium chloride, nitrate and acetylacetonate as precursors and the preparation routes employed were impregnation of alumina with solutions of these precursors and the polyol method, in which palladium deposition is carried in a liquid polyol, e.g. ethylene glycol. All catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), surface area measurements and temperature programmed desorption of O2 (TPD). Unsteady-state methane oxidation was carried out by temperature-programmed surface reaction (TPSR). The results obtained suggested that the use of different palladium precursors and preparation routes played an important role on the properties of the catalysts, as palladium particle size, thermal stability of PdO and catalytic properties toward methane combustion. The use of palladium acetylacetonate as precursor by the impregnation method generated well-dispersed PdO particles on alumina. Regarding the PdO thermal stability and the activity toward methane combustion, this catalyst also presented the highest thermal stability and catalytic activity.

The effect of precursor chemistry and preparation conditions on the formation of pore structure in metal-containing carbon fibers

Activated carbon fibers (ACFs) prepared from petroleum isotropic pitch and the same containing silver and cobalt nitrate, cobalt and palladium acetylacetonates, as well as mixtures of two salts with a total metal or metal mixture content of 1 wt% have been studied. The processing parameters are summarized for activated carbon fibers containing individual metals and metal mixtures. The results suggest that the generation of metal-containing particles and the formation of pore structure depend on many different factors including the composition of the metal and pitch precursors, the interaction of the metal and pitch precursors during the fiber production process, and the interaction between the two metal precursors when more than one metal salt is used. The addition of silver and cobalt in the form of nitrate salts enlarges the micropores and generates small mesopores with a narrow range of sizes. The addition of palladium as an acetylacetonate salt leads to the formation of both small micropores and larger mesopores. The cobalt additive as an acetylacetonate salt catalyzes the activation process, creating large mesopores and macropores. Mixing of two different metal precursors affects the particle composition and size. This, in turn, controls the pore structure of the final activated fibers. During activation, the two metal precursors can act independently (Ag/Co mixture). However, in other cases their effect can be additive (Co/Pd mixture), or even synergistic (Ag/Pd mixture).