Supported Pd Nanoparticles Research Articles

Organic/inorganic hybrid composed of modified polyacrylamide grafted silica supported Pd nanoparticles using RAFT polymerization process: Controlled synthesis, characterization and catalytic activity

Reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized for the preparation of polyacrylamide brushes grafted onto silica particles (SiO2-g-PAAm) via “grafting to” and “grafting from” approach in a controlled manner. Control of both the polymer's molecular weight and the density of grafted chains can be achieved by these methods. The polymer grafted silica was further modified to convert it to phosphinite ligand. Complexation of this ligand with Pd(OAc)2 was performed in order to obtain the Pd catalytic system. Various techniques such as FT-IR, TGA, XRD and electron microscopy systems such as SEM and TEM were conducted as characterization methods. Moreover, X-Ray photoelectron spectroscopy (XPS) of the catalyst disclosed the binding energy of Pd in zero oxidation state properly. This organic-inorganic hybrid catalytic system showed proper activity in Heck coupling reaction. The catalyst was successfully reused in repeating cycles with negligible change in its efficiency. Characteristic of the catalyst such as size and shape, chemicophysical stability and the structure of catalyst are retained almost unchanged even after successive reactions.

CuO nanorods supported Pd nanoparticles as high performance electrocatalysts for glucose detection

CuO nanorods supported Pd nanoparticles (CuO-Pd) are fabricated as highly active electrocatalysts. The current density for CuO-Pd is ca. 3.7 times than that of CuO and ca. 129.3 times of Cu(OH)2-Pd precursor towards glucose detection. Moreover, the CuO-Pd nanorods also display low detection limit, high sensitivity, wide linear range, fast response, high stability and anti-interference performance for glucose detection. The excellent electrocatalytic performance of CuO-Pd nanorods might be ascribed to the synergistic effect of CuO and noble metal Pd, which is promising for applications as nonenzymatic glucose sensors.

Supporting Pd nanoparticles on riboflavin-derived carbon: an efficient electrocatalyst for ethylene glycol oxidation

Nitrogen-containing carbon materials from sustainable chemicals are of great interest for energy conversion technology. As a natural, nontoxic, biological and economical compound, riboflavin is promising for designing and producing nitrogen-containing carbon support materials for fuel cells. Herein, a novel carbon material is obtained by H2SO4 pre-carbonized and heat treatment steps from riboflavin (riboflavin-derived carbon, named as R-C), which is used as support to immobilize Pd nanoparticles (Pd/R-C). The results show that, compared with conventional Pd/C prepared from XC-72R support, the Pd/R-C catalyst exhibits larger electrochemically active surface area (EASA) and higher electrocatalytic activity and stability towards ethylene glycol oxidation (EGOR). The effects of temperature scan rates, ethylene glycol, and KOH concentrations on EGOR are also investigated, respectively.

Graphene hydrogel supported palladium nanoparticles as an efficient and reusable heterogeneous catalysts in the transfer hydrogenation of nitroarenes using ammonia borane as a hydrogen source

Abstract Addressed herein is a facile one-pot synthesis of graphene hydrogel (GHJ) supported Pd nanoparticles (NPs), namely Pd-GHJ nanocomposites, via a novel method that comprises the combination of hydrothermal treatment and polyol reduction protocols in water. The structure Pd-GHJ nanocomposites were characterized by TEM, HR-TEM, XRD, XPS, Raman spectroscopy and BET surface area analysis. Then, Pd-GHJ nanocomposites were used as a heterogeneous catalysts in the tandem dehydrogenation of ammonia borane and hydrogenation of nitroarenes (Ar–NO2) to anilines (Ar–NH2) in the water/methanol mixture at room temperature. A variety of Ar–NO2 derivatives (total 9 examples) were successfully converted to the corresponding Ar–NH2 by the help of Pd-GHJ nanocomposites catalyzed tandem reactions with the conversion yields reaching up to 99% in only 20 min reaction time. Moreover, Pd-GHJ nanocomposites were demonstrated to be the reusable catalysts in the tandem reactions by preserving their initial catalytic performance after five consecutive catalytic cycles. It is believed that the presented synthesis protocol for the Pd-GHJ nanocomposites and the catalytic tandem hydrogenation reactions will make a significant contribution to the catalysis and synthetic organic chemistry fields.

An Explosive Bomb-Inspired Method to Prepare Collapsed and Ruptured Fe2 O3 /Nitrogen-Doped Carbon Capsules as Catalyst Support.

Compared with integrated capsules, ruptured ones have better mass diffusion and transport properties due to large gaps in the shells. However, most studies focus on integrated capsules, whereas little attention has been paid to the ruptured counterparts. Herein, an explosive bomb-inspired method was employed to prepare collapsed and ruptured Fe2 O3 /nitrogen-doped carbon (CR-Fe2 O3 /NC) capsules by using polystyrene (PS) nanoparticles (NPs) as a hard template, and polypyrrole (PPy) with embedded Prussian blue (PB) NPs as the shell. During pyrolysis, PB is converted into Fe2 O3 , and PPy is carbonized to form NC. Importantly, the PS core decomposes into gas molecules, leading to high pressure inside of the capsule, which explodes the thin shell into pieces. The roles of shell thickness and amount of Fe2 O3 on determining the spherical or collapsed, and integrated or ruptured morphology were revealed. Taking advantage of structural merits, including large gaps, thin shells, low density, and high surface area, CR-Fe2 O3 /NC capsules were used as supports for Pd NPs. These capsules exhibited better catalytic activity than that of integrated ones. Due to the magnetic properties, they could be reused at least five times.

Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene

Pd/C catalysts were prepared by deposited Pd nanoparticles (NPs) on different carbon supports including activated carbon (AC), graphite oxide (GO), and reduced graphite oxide (rGO) using sol-immobilization method. Through transmission electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.

One-step synthesis of Pd-NPs@Cu2(BDC)2DABCO as efficient heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction

A new heterogeneous palladium catalyst has been synthesized by one-step encapsulation in nanoporous metal-organic framework Cu2(BDC)2(DABCO) (BDC = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane) under a temperature control program. Supported Pd nanoparticles (Pd-NPs@Cu2(BDC)2(DABCO)) were characterized by X-ray diffraction, BET analysis, field emission scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission and X-ray photoelectron spectroscopy (XPS). The Highly dispersed Pd particles (Pd-NPs@Cu2(BDC)2(DABCO)) offered a very efficient catalytic activity towards the Suzuki–Miyaura cross-coupling reaction.

Palladium Nanoparticles Anchored on Anatase Titanium Dioxide‐Black Phosphorus Hybrids with Heterointerfaces: Highly Electroactive and Durable Catalysts for Ethanol Electrooxidation

AbstractDesigning high‐performance palladium (Pd) supports with enhanced ethanol oxidation reaction (EOR) activity has consistently been a challenge. Here, a novel anatase titanium dioxide nanosheets‐black phosphorus (ATN‐BP) hybrid is fabricated as a support for Pd nanoparticles used in the EOR. The direct ball‐milling of BP nanoflakes and ATN under argon protection lead to the formation of ATN‐BP hybrids with BP nanoflakes interconnected by cataclastic ATN with POTi bonds. The structure of ATN‐BP not only is beneficial for improving the electrolyte penetration and electron transportation but also has a strong influence on the stripping of reactive intermediates through the synergistic interaction between Pd and ATN‐BP. The results demonstrate that the Pd/ATN‐BP hybrids with heterointerfaces of Pd, BP, and ATN exhibit ultrahigh electroactivity and durability. In the EOR, the Pd/ATN‐BP catalyst can achieve an electrochemically active surface area of ≈462.1 m2 gPd−1 and a mass peak current density of 5023.8 mA mgPd−1, which are 11.67 and 6.87 times greater, respectively, than those of commercial Pd/C. The Pd/ATN‐BP catalysts also show remarkable stability with a retention rate of the peak current density of ≈30.6% after a durability test of 3600 s.

Microwave-activated dehydrogenation of perhydro-N-ethylcarbazol over bimetallic Pd-M/TiO2 catalysts as the second stage of hydrogen storage in liquid substrates

Reversible catalytic hydrogenation–dehydrogenation of aromatic and heterocyclic compounds is considered as a promising approach to hydrogen storage. While exploring the microwave-assisted catalytic processes, the Pd/TiO2 catalysts were shown to be most effective. The catalytic activity of the Pd/TiO2 system can be enhanced by introduction of a second metal after the formation of the supported Pd nanoparticles, with Pt and Ru acting as most efficient promoters. The studies of the catalytic behavior of the supported bimetallic Pd–Ru/TiO2 and Pd–Pt/TiO2 catalysts in perhydro-N-ethylcarbazole (H-NEC) dehydrogenation revealed that the catalytic activity under microwave activation is higher than that in a conventional thermal mode at the same reaction temperatures. Complete dehydrogenation occurred only under microwave activation, with a negligible by-product formation. This feature of the catalysts makes possible their application in the hydrogen storage systems based on the reversible hydrogenation–dehydrogenation cycles under microwave activation.

C–H Arylation of 2-Phenylpyridines on Carbon Nanotube Supported Pd Nanoparticles

C–H Arylation of 2-Phenylpyridines on Carbon Nanotube Supported Pd Nanoparticles

Nitrogen-doped carbon black supported Pd nanoparticles as an effective catalyst for formic acid electro-oxidation reaction

Pd nanoparticles supported on nitrogen doped carbon black (Vulcan XC-72R) with two different levels of doping were prepared by the microwave-assisted ethylene glycol reduction process and used as catalyst for the formic acid electro-oxidation (FAEO). The results indicate that the different nitrogen doping contents in Pd/N-C catalysts have a significant effect on the performance of FAEO. A higher N content facilitates the uniform dispersion of Pd nanoparticles on carbon black with narrow particle size distribution. Furthermore, the electrochemical results show that the catalyst with a higher N-doping content possesses a higher catalytic activity and a long-term stability for FAEO. The peak current density of the Pd/N-C (high) catalyst is 1.27 and 2.31 times that of the Pd/N-C (low) and homemade Pd/C-H catalyst. The present paper may provide a simple method for preparation of high-performance anode catalyst for direct formic acid fuel cells (DFAFCs).

Trace iron impurities deactivate palladium supported on nitrogen-doped carbon nanotubes for nitrobenzene hydrogenation

Nitrogen-doped carbons can effectively stabilize noble metal particles to achieve high catalytic performances. However, the metallic impurities in carbon nanomaterials, e.g. the residual growth catalysts of carbon nanotubes (CNTs), have some unforeseen effects on the catalysis involving nanocarbons. Herein, we demonstrate that the residual growth catalysts of N-doped CNTs (NCNTs) may significantly deactivate Pd catalysts for the hydrogenation of nitrobenzene. Through high-resolution transmission electron microscopy and CO-stripping, it was determined that the N dopants improved the dispersion of Pd nanoparticles. However, the iron, at ppm level, in residual catalysts encapsulated inside NCNTs can transfer onto the surface of Pd to block active sites so that the activity of Pd/NCNTs was much lower than that of Pd/CNTs. The similar effect was observed for most of the common metallic impurities in carbon materials, including Co, Ni, Mn, Cr, Cu, Zn, Mo, Al and Mg. To exploit the N-doped carbons, we deposited N-doped carbon layers on purified CNTs through pyridine pyrolysis and then supported Pd nanoparticles. By this means, the activity of Pd for nitrobenzene hydrogenation was improved by 3.85 folds compared to conventional CNTs, emphasizing the importance of controlling impurities in N-doped carbon materials for high performance catalysts.

3D porous Cu@Cu2O films supported Pd nanoparticles for glucose electrocatalytic oxidation

3D hierarchically porous Cu@Cu2O films supported Pd nanoparticles with excellent electrocatalytic activity are synthesized through electrochemical deposition, anodic oxidation and redox growth. Enzyme-free glucose biosensors based on the porous Cu@Cu2O-Pd electrodes exhibit higher sensitivity (1.157mAcm−2mM−1) than those of the porous Cu@Cu2O films (0.607mAcm−2mM−1), porous Cu films (0.507mAcm−2mM−1) and Pd nanoparticles (0.107mAcm−2mM−1). The enhanced activity of the porous Cu@Cu2O-Pd nanostructures might be attributed to the unique hierarchical porous structures with highly exposed active sites and synergetic effect from metal oxide semiconductor Cu2O and noble metal Pd.

High surface area Pd nanocatalyst on core-shell tungsten based support as a beneficial catalyst for low temperature fuel cells application

Tungsten based support was prepared by polycondensation of resorcinol and formaldehyde from ammonium metatungstate, in the presence cetyltrimethylammonium bromide (CTABr) surfactant. Pd nanocatalyst on this support was synthesized by borohydride reduction method. The obtained materials were characterized by High Resolution Transmission Electron Microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), X-ray Photoelectron Spectroscopy (XPS) and electrochemical measurements. TEM analysis revealed Pd nanoparticles size in the range of a few nanometers, even the clusters of single Pd atoms. X-Ray Photoelectron Spectroscopy was applied to determine surface composition of the substrates. It was found that tungsten based support consisted of W, WC and WO3 species. The presence of metallic palladium – Pd(0) in the Pd/W@WCWO3 catalyst was revealed, as well. The catalytic activity and stability for the oxygen reduction were investigated in acid and alkaline solutions, by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. The catalystsʹ activities were compared to the carbon supported Pd nanoparticles (Vulcan XC 72). WC supported Pd nanoparticles have shown high activity and superior stability, comparable even to Pt based catalysts, especially in alkaline electrolytes.

ZnO-template synthesis of rattle-type catalysts with supported Pd nanoparticles encapsulated in hollow ZIF-8 for liquid hydrogenation

MOFs-based yolk-shell composites are newly-presented but promising catalysts in the area of catalysis. In this work, a kind of unique rattle-type Pd/ZnO@hollow ZIF-8 yolk-shell catalyst is developed via a ZnO-template approach, in which there exist two processes of both ZnO-induced ZIF-8 formation and ZnO dissolution. Of prime importance is that ZnO was selected as the sacrificial template since it can not only be etched in the solution of ligands but also assist the formation of compact ZIF-8 shell by providing nucleation sites via linker activation. It is also proposed that sufficient amount of Zn(NO3)2·6H2O and 2-methylimidazole added in the growth solution of ZIF-8 should accelerate the outward growth of ZIF-8 layer as well as dissolution of ZnO. This way, the final construction of Pd/ZnO@hollow ZIF-8 yolk-shell materials is achieved. Compared to the Pd/ZnO counterparts, Pd/ZnO@hollow ZIF-8 rattle-type catalysts demonstrate a promoted behavior in terms of size-selectivity for the liquid hydrogenations of alkenes due to the outer ZIF-8 shell acting as a molecular sieve. It can also protect the catalytically active Pd NPs from poisoning and leaching, giving rise to an excellent stability. Moreover, the yolk-shell catalysts manifest a better activity beyond their core-shell counterparts since the presented interior hollow space between core and shell is likely to expose more active surfaces to reactants.

A Facile Route for Production of CexOy Modified Carbon Fiber Supported Pd Nanoparticles and Their Highly Efficient Catalytic Activity for Heck Reaction

The highly-efficient carbon nanofibers supported CexOy–Pd NPs catalyst for catalyzing the Heck reaction by the electrospinning technique, hydrogenation reduction and subsequent calcination processes were prepared. The CexOy–Pd NPs/CNFs have enhanced catalytic activity compared with the Pd NPs/CNFs. The CexOy could play an auxiliary role in the catalytic process.

Highly efficient reusable Pd nanoparticles based on eggshell: Green synthesis, characterization and their application in catalytic reduction of variety of organic dyes and ligand-free oxidative hydroxylation of phenylboronic acid at room temperature

This work reports the use of eggshell as economic and environmentally friendly support for preparation of the supported Pd nanoparticles (Pd NPs) through the green and simple in situ reduction method using barberry fruit extract as a reducing and stabilizing agent. The catalytic activity of the as-prepared catalyst was observed in the ligand-free hydroxylation of phenylboronic acid to phenol and reduction of various organic dyes, such as 4-nitrophenol (4-NP), Methyl orange (MO), Congo red (CR) and Methylene blue (MB) in the presence of NaBH4 in water at room temperature. The synthesized nanocomposite was characterized by XRD, SEM, EDS and TEM. Additionally, this nanocomposite can be recycled and showed good catalytic ability and excellent recyclability. © 2016 Elsevier Science. All rights reserved.

Wrinkled mesoporous carbon supported Pd nanoparticles for hydrogenation and aerobic oxidation reactions

Wrinkled mesoporous silica (WMS) was employed as a hard template to synthesize a carbon replica. The resulting carbon materials, wrinkled mesoporous carbon (WMC), retained the main structural features from the WMS, which has conical pores that radiate from the center of the spherical particle to the outer surface in all directions resulting in wrinkled shaped pore walls. This WMC material was used as a catalyst support for Pd nanoparticles. The Pd on WMC catalyst showed superior performance over commercial Pd on activated carbon for both styrene hydrogenation and the aerobic oxidation of benzyl alcohol.

Visible-light-enhanced photocatalytic Sonogashira reaction over silicon carbide supported Pd nanoparticles

Sonogashira reaction of aryl halides with terminal alkynes can be realized by a visible-light-driven heterogeneous catalytic route using silicon carbide supported Pd nanoparticles as the catalyst under copper-, and ligand-free conditions. Under the irradiation of visible light, the photo-generated electrons excited in SiC can quickly transfer to Pd nanoparticles through the Mott-Schottky contact, and make them electron-rich. The electrons of Pd particles become energetic by absorbing the energy of visible light, and then transfer to halogen atoms to facilitate the cleavage of carbon-halogen bond in aryl halides. The final carbon-carbon formation is achieved by the substitution reaction and reductive elimination processes.

Mesoporous silica-based nanotubes loaded Pd nanoparticles: Effect of framework compositions on the performance in heterogeneous catalysis

Well-shaped mesoporous silica-based nanotubes with different framework compositions, such as organic groups (ethylene, phenylene), carbon/silica hybrids, could be controllably synthesized with the inner diameter of less than 10 nm and the surface areas of about 400–900 m2 g−1. Through an impregnation-reduction process, palladium (Pd) nanoparticles have been uniformly dispersed in the channels of these different nanotubes, which were confirmed by electron microscopy analysis. The catalytic performance of these silica-based nanotubes loaded Pd nanoparticles was evaluated by the aerobic oxidation of benzyl alcohol and enantioselective hydrogenation of α,β-unsaturated carboxylic acid, respectively. Due to one-dimensional nanotube structures and tunable hydrophilic/hydrophobic properties, the organosilica nanotubes supported Pd nanoparticles could afford >99% conversion of benzyl alcohol and 89% selectivity of benzaldehyde within 2 h. Importantly, carbon/silica hybrid nanotubes may have a positive effect on the reaction, which gave about 95% selectivity of benzaldehyde. The catalysts could be reused without an obvious decrease in both conversion and selectivity. Furthermore, the silica-based nanotubes supported Pd nanoparticles were also efficient for asymmetric hydrogenation of α,β-unsaturated carboxylic acids, which showed a highest conversion of 99% with 48% enantioselectivity.