Deposition Of Palladium Nanoparticles Research Articles

2D Materials for the Electro Oxidation of Formic Acid

In recent years Direct Formic Acid Fuel Cells (DFAFCs) have attracted interest as alternative energy sources. Formic acid is abundant as it is a by-product of multiple industrial processes and it can be obtained from the oxidation of biomass. In addition, due to the capacity to use high concentrations of fuel, DFAFCs are effective at room temperature which makes it an ideal candidate for portable energy applications and it has a low permeability, which clearly distinguishes it from other Proton Exchange Membrane Fuel Cells (PEMFCs). This allows it to generate higher power densities ~160 mW/cm2 at room temperature outperforming other liquid fuel cells such as Direct Methanol Fuel Cells (DMFCs) with power densities of ~50 mW/cm2. However, a few obstacles prevents its optimization, first the behaviour and loading of the catalytic material and second the proper selectivity of the proton exchange membrane. For this the synthesis of a new catalytic material has been carried out, by the deposition of palladium Nano-particles in graphene oxide and reduced graphene oxide, obtained by the electrochemical exfoliation of graphite in order to introduce doping agents in the graphene matrix such as nitrogen, sulphur and boron and with it improve its catalytically activity and reduce catalyst loadings in DFAFCs. To address the second obstacle hindering DFAFCs, a comparative analysis of proton exchange membranes of the Nafion family was carried out and the intrinsic conductivity, dimensional stability as well as its operational temperature was observed for its use in formic acid fuel cells. From the results obtained a high performance was observed using a polytetrafluoroethylene reinforce membrane (Nafion XL) at room temperature. The membrane displayed a higher resistance to dimensional change when exposed to a wide range of formic acid concentrations, showing a maximum increase of 10% of its planar dimension while other membranes such as Nafion 117,115 and 211 had a significantly higher increase up to 45%. Results indicated that a reinforced membrane could be more suitable for DFAFCs, not only by possessing a higher dimensional stability but also due to it having a higher hydrophobicity due to the reinforcement and the lower content of sulfonic groups present in the copolymer. These changes would address the dehydration of the membrane, a factor substantially affecting the performance of the cell.

Facile Fabrication of Highly Active Magnetic Aminoclay Supported Palladium Nanoparticles for the Room Temperature Catalytic Reduction of Nitrophenol and Nitroanilines

Magnetically recyclable nanocatalysts with excellent performance are urgent need in heterogeneous catalysis, due to their magnetic nature, which allows for convenient and efficient separation with the help of an external magnetic field. In this research, we developed a simple and rapid method to fabricate a magnetic aminoclay (AC) based an AC@Fe3O4@Pd nanocatalyst by depositing palladium nanoparticles (Pd NPs) on the surface of the magnetic aminoclay nanocomposite. The microstructure and the magnetic properties of as-prepared AC@Fe3O4@Pd were tested using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM) analyses. The resultant AC@Fe3O4@Pd nanocatalyst with the magnetic Fe-based inner shell, catalytically activate the outer noble metal shell, which when combined with ultrafine Pd NPs, synergistically enhanced the catalytic activity and recyclability in organocatalysis. As the aminoclay displayed good water dispersibility, the nanocatalyst indicated satisfactory catalytic performance in the reaction of reducing nitrophenol and nitroanilines to the corresponding aminobenzene derivatives. Meanwhile, the AC@Fe3O4@Pd nanocatalyst exhibited excellent reusability, while still maintaining good activity after several catalytic cycles.

Enhanced visible light-induced photocatalytic activity of surface-modified BiOBr with Pd nanoparticles

Abstract Palladium nanoparticles well-dispersed on BiOBr surfaces were successfully prepared via a two-step process, namely hydrothermal synthesis of BiOBr followed by photodeposition of palladium. Surface-exposed palladium nanoparticles may improve the harvesting capacity of visible light photons via the surface plasmonic resonance effect to produce extra electrons. Palladium is an excellent electron acceptor, and therefore favours the separation of photogenerated electron/hole pairs. As a result, palladium significantly improves the photocatalytic activity of BiOBr in the removal of organic pollutants (phenol) under visible light irradiation. In addition to as-prepared samples which were comprehensively characterized, the mechanism for the enhancement via the deposition of palladium nanoparticles was also proposed based on results. This work may serve as solid evidence to confirm that surface-deposited palladium nanoparticles are capable of improving photocatalytic activity, and that photodeposition may be an effective approach to load metal nanoparticles onto a surface.

Palladium nanoparticle and decorated carbon nanotube for electrochemical hydrogen storage

This study proposes a multicomponent system for hydrogen storage. An electrochemical evaluation was used as a simple and accurate technique to assess the storage capacity. A porous silicon substrate was fabricated using an electrochemical anodization process and decorated with palladium nanoparticles using the electroless method. The hybrid substrate underwent chemical vapor deposition for 45 min. Since the deposited palladium nanoparticles could act as potential catalysts, carbon nanotubes grew properly over hybrid structure. The final sample was obtained through post-treatment by palladium nanoparticles using the same electroless method. This triplet sample was characterized using field emission scanning electron microscopy and X-ray diffraction. Galvanostatic charge/discharge experiments were used to conduct electrochemical evaluations of proposed electrode. A maximum hydrogen storage capacity of 537 mAh/g (∼2.05 wt.%) was achieved for the triple-structure sample. The measurements demonstrate that the storage capacity of the triple-structure sample was reduced by a factor of 0.05% after 100 cycles. Although the obtained storage capacity is far from DOE targets, optimized structures based on the proposed electrode may be further developed as an efficient storage system.

High Performance Palladium Supported on Nanoporous Carbon under Anhydrous Condition.

Due to the high cost of polymer electrolyte fuel cells (PEFCs), replacing platinum (Pt) with some inexpensive metal was carried out. Here, we deposited palladium nanoparticles (Pd-NPs) on nanoporous carbon (NC) after wrapping by poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole] (PyPBI) doped with phosphoric acid (PA) and the Pd-NPs size was successfully controlled by varying the weight ratio between Pd precursor and carbon support doped with PA. The membrane electrode assembly (MEA) fabricated from the optimized electrocatalyst with 0.05 mgPd cm−2 for both anode and cathode sides showed a power density of 76 mW cm−2 under 120 °C without any humidification, which was comparable to the commercial CB/Pt, 89 mW cm−2 with 0.45 mgPt cm−2 loaded in both anode and cathode. Meanwhile, the power density of hybrid MEA with 0.45 mgPt cm−2 in cathode and 0.05 mgPd cm−2 in anode reached 188 mW cm−2. The high performance of the Pt-free electrocatalyst was attributed to the porous structure enhancing the gas diffusion and the PyPBI-PA facilitating the proton conductivity in catalyst layer. Meanwhile, the durability of Pd electrocatalyst was enhanced by coating with acidic polymer. The newly fabricated Pt-free electrocatalyst is extremely promising for reducing the cost in the high-temperature PEFCs.

Highly Efficient Fuel Cell Electrodes from Few-Layer Graphene Sheets and Electrochemically Deposited Palladium Nanoparticles

An extremely efficient ethanol fuel cell electrode is produced by combining the large surface area of vertically oriented and highly conductive few-layer graphene sheets with electrochemically deposited palladium nanoparticles. The electrodes show an extraordinary high catalyst activity of up to 7977 mA/(mg Pd) at low catalyst loadings of 0.64 $\mu$g/cm$^2$ and a very high current density of up to 106 mA/cm$^2$ at high catalyst loadings of 83 $\mu$g/cm$^2$. Moreover, the low onset potentials combined with a good poisoning resistance and long-term stability make these electrodes highly suitable for real applications. These features are achieved by using a newly developed electrochemical catalyst deposition process exploiting high voltages of up to 3.5 kV. This technique allows controlling the catalyst amount ranging from a homogeneous widespread distribution of small ($\leq$ 10 nm) palladium nanoparticles to rather dense layers of particles, while every catalyst particle has electrical contact to the graphene electrode.

PdNP Decoration of Halloysite Lumen via Selective Grafting of Ionic Liquid onto the Aluminol Surfaces and Catalytic Application.

The synthesis of selectively deposited palladium nanoparticles (PdNPs) inside tubular halloysite lumens is reported. This specific localization was directed by the selective modification of the aluminol surfaces of the clay mineral through stable Al-O-C bonds. An ionic liquid (1-(2-hydroxyethyl)-3-methylimidazolium) was grafted onto halloysite following the guest displacement method (generally used for kaolinite) using halloysite-DMSO preintercalate. The characterization of this clay nanohybrid material (XRD, NMR, TGA) showed characteristics reminiscent of similar materials synthesized from kaolinite. The grafting on halloysite lumens was also effective without using the DMSO preintercalate. The presence of these new functionalities in halloysite directs the synthesis of uniform PdNPs with size ranging between 3 and 6 nm located exclusively in the lumens. This results from the selective adsorption of PdNPs precursors in functionalized lumens through an anion exchange mechanism followed by in situ reduction. In contrast, the unmodified clay mineral displayed nanoparticles both inside and outside the tubes. These catalysts showed significant catalytic activity for the reduction of 4-nitrophenol (4-NP). The most efficient catalysts were recycled up to three times without reducing significantly the catalytic activities.

Fabrication of palladium nanoparticles immobilized on an amine-functionalized ceramic membrane support using a nanoparticulate colloidal impregnation method with enhanced catalytic properties

An efficient and reusable catalyst was developed by depositing palladium nanoparticles on an amine-functionalized ceramic membrane support using a nanoparticulate colloidal impregnation method. The as-prepared Pdloaded ceramic membrane support was characterized by XRD, SEM, EDS, TEM, XPS, ICP, and its catalytic properties were investigated in the liquid-phase p-nitrophenol hydrogenation. A comparative study was also made with the palladium nanoparticles deposited on an amine-functionalized ceramic membrane support by an impregnation-reduction method. The palladium nanoparticles could be homogeneously immobilized on the ceramic membrane support surface, and exhibited excellent catalytic performance in the p-nitrophenol hydrogenation. The catalytic activity of the Pdloaded ceramic membrane support prepared by the nanoparticulate colloidal impregnation method increased by 16.6% compared to that of impregnation-reduction method. In the nanoparticulate colloidal impregnation method, palladium nanoparticles were presynthesized, higher loading of Pd(0) could be obtained, resulting in better catalytic activity. The as-prepared Pd-loaded ceramic membrane support could be easily reused for several cycles without appreciable degradation of catalytic activity.

Xylan-type hemicellulose supported palladium nanoparticles: a highly efficient and reusable catalyst for the carbon–carbon coupling reactions

A heterogeneous catalyst was prepared by depositing palladium nanoparticles onto xylan-type hemicellulose, which is a kind of renewable biopolymer catalyst, and used as an efficient and recyclable catalyst for the Suzuki, Heck, and Sonogashira cross-coupling reactions.

Deposition of palladium nanoparticles in SBA-15 templated silica using supercritical carbon dioxide

Preparation of supported nanoparticles by palladium deposition onto silica (SBA-15) from a solution of tris(dibenzylideneacetone) dipalladium(0) (Pd2(dba)3) in supercritical carbon dioxide (scCO2) was successfully achieved. Pd2(dba)3 avoided agglomeration of nanoparticles, which is typically associated with secondary processes including reduction of metal salts. scCO2 impregnation was superior at depositing palladium nanoparticles within the porous channels of SBA-15, as compared to organic solvents. The resulting material demonstrated significant potential for use in catalytic applications including hydrogenations and showed specific selectivity towards alkene hydrogenation.

Electrochemical synthesis and characterization of palladium nanoparticles on nafion–graphene support and its application for Suzuki coupling reaction

The electrochemically deposited palladium nanoparticles on nafion–graphene support showed an excellent catalytic activity for Suzuki coupling reactions. The as obtained catalyst was characterized by SEM, TEM, EDAX, XRD, and TGA. The particle size of palladium nanoparticles (Pd NPs) determined from TEM was in the range of 4–12 nm. The mean diameter of Pd NPs was found to be 8.1 ± 1.9 nm. The recyclability of the catalyst was examined and it did not show any significant loss of catalytic activity for five consecutive cycles.

Preparation of Palladium Nanoparticles Deposited on a Silanized Hollow Fiber Ceramic Membrane Support and Their Catalytic Properties

An efficient and reusable catalyst was developed by depositing palladium nanoparticles on a hollow fiber ceramic membrane support in which the support surface was silanized with aminofunctional silane. In the present work, the hollow fiber ceramic membrane support was used for catalyst immobilization only. The as-prepared Pd-loaded hollow fiber ceramic membrane support was extensively characterized by ICP, FESEM, EDS, XPS, and HRTEM, and the hydrogenation of p-nitrophenol to p-aminophenol was used as a model reaction to evaluate its catalytic properties. For comparison the palladium nanoparticles were also deposited on a tubular ceramic membrane support. The catalytic activity of Pd-loaded hollow fiber ceramic membrane support is significantly higher than that of Pd-loaded tubular ceramic membrane support. The hollow ceramic fibers can provide more membrane area for the deposition of palladium nanoparticles at the same volume of membrane module, and a higher palladium loading is obtained, and their pore s...

Comparative Investigation of Chemical Vapor Deposition of Palladium Nanoparticles on Different Carbon Substrates

The effects of different sulfur-doped carbon substrates including single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), and activated carbon were compared for deposition of palladium nanoparticles synthesized by chemical vapor deposition method. Electron microscopy, spectroscopic techniques, and thermogravimetric analysis were used for characterization of palladium nanoparticles doped on carbon substrates. The results demonstrated that under similar conditions, the average diameter of palladium nanoparticles was ∼10 nm for SWCNTs, 40 nm for MWCNTs, 100 nm for CNFs, and 250 nm for carbon. The relative standard deviations of the quantity of deposited palladium nanoparticles on each carbon substrate for six replicate depositions were 1.24% for SWCNTs, 1.67% for MWCNTs, 1.83% for CNFs, and 2.16% for carbon.

Electrochemical sensing platform based on palladium modified ceria nanoparticles

Palladium modified cerium oxide (CeO 2 or ceria) nanoparticles (Pd-CeO 2) were prepared by depositing palladium nanoparticles with average diameters of 3–5 nm on the surface of CeO 2 via chemical reduction of the precursor (Pd 2+). The electrocatalytic activity of Pd-CeO 2 toward the detection of different important compounds (i.e. glucose, ascorbic acid (AA), dopamine (DA) and uric acid (UA)) has been investigated. Compared with the CeO 2 or Pd modified electrode, the Pd-CeO 2 modified electrode has higher catalytic activity toward the oxidation of glucose, AA, DA, and UA. A nonenzymatic glucose sensor was developed for the sensitive and selective detection of glucose. Moreover, in the mixture of AA, DA and UA, obvious electrochemical potential separations among the three detected peaks were observed, making the simultaneously determination of AA, DA and UA possible. The attractive features of Pd-CeO 2 provide potential applications in sensor and biosensor design.

Nonenzymatic glucose sensing based on deposited palladium nanoparticles on epoxy-silver electrodes

A new approach for nonenzymatic glucose sensing, based on a simple modification of epoxy-silver surfaces deposited on the tip of commercial copper electric wires, is presented. Palladium was galvanically displaced on the surface of the epoxy-silver surface in order to obtain metal nanoparticles that act as catalyst for the direct oxidation of glucose. Scanning electron microscopy revealed the formation of the metal nanoparticles. X-ray photoelectron spectroscopy confirmed the metallic nature of the formed nanostructures on the surface. Electrochemical characterization and calibration of the palladium-modified epoxy-silver electrode is reported, obtaining a linear range of 1–20 mM for the detection of glucose with low interference of ascorbic acid and uric acid. A simple 3-step coulometry was used as the detection technique. The developed sensing material is believed to be a great candidate for integration in small devices for clinical essays, due to the simplicity and cost effectiveness of the presented approach, compared to the state-of-the-art devices reported recently in the literature. Simplicity in the coulometry determinations makes these Pd-modified epoxy-silver sensors a good candidate for easy glucose determinations.

Reactive Deposition of Palladium Nanoparticles onto Zeolite Membranes in Supercritical CO2

Pd/Si-MFI membranes are fabricated by depositing palladium nanoparticles onto Si-MFI membranes via opposing reactants chemical fluid deposition in supercritical carbon dioxide. Palladium hexafluoroacetylacetonate [Pd(hfac)2] and ethanol are used as the Pd precursor and the reducing agent, respectively, in the deposition process. The resulting Pd/Si-MFI membrane is characterized using SEM, XRD, EPMA, TEM, and EDX techniques. It is demonstrated that a continuous layer of Pd particles with size of 10 nm is covered on the matrix surface while 30-nm Pd particles are plugged into the defects within the matrix. The H2/N2 permselectivity has been significantly increased due to the deposition of Pd nanoparticles in the Si-MFI membrane, which could keep stable below the critical temperature. This bifunctional membrane and similar membranes possess the application potential to achieve various one-step syntheses.

Positioning Pd catalyst particles for carbon nanotube growth using charge patterns created with a scanning electron microscope

Positioning of charged nanoparticles with the help of charge patterns in an insulator substrate is a known method. However, the creation of charge patterns with a scanning electron microscope for this is relatively new. Here a scanning electron microscope is used for the creation of localized charge patterns in an insulator, while a glowing wire generator is used as the nanoparticle source. The deposited palladium nanoparticles are used as catalysts for the localized growth of carbon nanotubes in a chemical vapor deposition oven. The authors show first the results on local carbon nanotube growth using this procedure.

Nonenzymatic Electrochemical Detection of Glucose Based on Palladium−Single-Walled Carbon Nanotube Hybrid Nanostructures

A new electrocatalyst, palladium nanoparticle-single-walled carbon nanotube (Pd-SWNTs) hybrid nanostructure, for the nonenzymatic oxidation of glucose was developed and characterized by X-ray diffraction (XRD) and the transmission electron microscope (TEM). The hybrid nanostructures were prepared by depositing palladium nanoparticles with average diameters of 4-5 nm on the surface of single-walled carbon nanotubes (SWNTs) via chemical reduction of the precursor (Pd(2+)). The electrocatalyst showed good electrocatalytic activity toward the oxidation of glucose in the neutral phosphate buffer solution (PBS, pH 7.4) even in the presence of a high concentration of chloride ions. A nonenzymatic amperometric glucose sensor was developed with the use of the Pd-SWNT nanostructure as an electrocatalyst. The sensor had good electrocatalytic activity toward oxidation of glucose and exhibited a rapid response (ca.3 s), a low detection limit (0.2 +/- 0.05 microM), a wide and useful linear range (0.5-17 mM), and high sensitivity (approximately 160 microA mM(-1) cm(-2)) as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid, 4-acetamidophenol, 3,4-dihydroxyphenylacetic acid, and so forth did not cause any interference due to the use of a low detection potential (-0.35 V vs SCE). The sensor can also be used for quantification of the concentration of glucose in real clinical samples. Therefore, this work has demonstrated a simple and effective sensing platform for nonenzymatic detection of glucose.

Deposition of Palladium Nanoparticles on Self-Assembled, Zinc-Induced Tubulin Macrotubes and Sheets

Co-factors control the GTP-induced assembly of tubulin protein into a variety of superstructures with defined geometry at the nanometre scale: microtubules, macrotubes, sheets, or spirals/rings. We report the Zn2+ ion-induced assembly of tubulin protein into sheet-like or tubular structures. Free functional groups of amino acids on the surface of the protein biopolymer provide nucleation sites for further deposition of small metal nanoparticles. This study describes the synthesis of metal particle--protein hybrids by a two-step chemical process that directs metal nanoparticle nucleation at specific surface sites by applying these tubulin assemblies as biotemplates. The hybrids are characterized by transmission electron microscopy (TEM) and scanning force microscopy (SFM). The present study demonstrates the potential and general applicability of tubulin assemblies as tools for the nanofabrication of nanoparticle arrays exhibiting various geometries.

Deposition of Pd Nano-Particles in W/O Microemulsion by Chemical Demulsifying

Palladium nano-particles were synthesized by W/O microemulsion composed of nonionic surfactant (alkylpolyglycol ethers) named Marlipal O13/50, water and cyclohexane. The deposition of palladium nano-particles by chemicals demulsifying was investigated. The results showed that the sequence of deposition rate of palladium nano-particles from microemulsion under the action of different chemical demulsifier is 1,4-dioxaneTHFmethanolethanoln-butanol. The effects on interfacial tension and amphiphilicity of chemical demulsifier were studied. The results showed that the demulsifying process of microemulsion is also a process of interfacial tension increasing and a process gradually near to Lifschitz line.