Well-dispersed Palladium Nanoparticles Research Articles

Pillar[5]arene-Derived Terpyridinepalladium(II) Complex: Synthesis, Characterization, and Application in Green Catalysis

Metal nanoparticle catalysts have attracted great interest because they possess high surface-to-volume ratios and exhibit a very large number of catalytically active sites per unit area. However, high surface-to-volume ratios will induce nanoparticle aggregates during the catalytic reactions, making them lose their catalytic activity. In this work, a monoterpyridine-unit-functionalized pillar[5]arene (TP5) was synthesized successfully, which can be used as anchoring sites for the controllable preparation of well-dispersed palladium nanoparticles [TP5/Pd(0) NPs]. The as-prepared TP5/Pd(0) NPs were fully characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, and powder X-ray diffraction. Importantly, the ultrafine TP5/Pd(0) NPs are found to be excellent and reusable catalysts for the reduction of nitrophenols in aqueous solution.

The effects of alkali metal ions on the physiochemical and catalytic properties of Pd/NiAlOx catalysts for lean methane oxidation

Self-assembled nickel-aluminum mixed oxides (NiAlOx) were prepared by using alkali metal ions as modifiers in a hydrothermal system and employed as the support materials for palladium catalysts. Via tuning the preparation procedure, both the ‘bonded’ and ‘deposited’ alkali metal ions were introduced to the NiAlOx materials for elucidating their effects on the physiochemical and the catalytic properties of Pd/NiAlOx catalysts for lean methane oxidation. Benefiting from the well-dispersed palladium nanoparticles, optimized electronic state of palladium phases, and the favorable structure of host materials, the optimal Pd/NiAl-Na sample exhibited excellent catalytic performance for methane oxidation. Over this sample, complete methane conversion was realized at 401 °C in the presence of 15 vol % water vapor, which was 26 °C lower than that of the Pd/NiAl catalyst (427 °C) at same reaction conditions. Due to the relatively small size of Li+ ions, certain amounts of Li+ incorporated into the NiAlOx lattice and improved the redox properties of NiAl-Li. However, its supported palladium catalysts did not show improved performance in the oxidation of methane. Furthermore, systematic characterizations revealed that the ‘deposited’ alkali metal ions resulted in the agglomeration of palladium nanoparticles and the formation of electron-deficient palladium component, thus exerting negative effect on the activities of palladium phases. It was hoped that this work could provide some fundamental understandings on the roles of alkali metal played in catalytic reaction.

Microwave-assisted synthesis of palladium nanoparticles using Frankincense resin and evaluation of their catalytic properties

The present study describes a microwave-assisted synthesis of well-dispersed palladium nanoparticles (PdNPs). For the first time,Frankincense resin (FR) obtained from the tree of Boswellia sacra is explored for the preparation of PdNPs. This method is rapid, inexpensive and devoid of toxic chemicals. FR aqueous extract with reducing polysaccharides and other phytochemicals served as an effective reducing and stabilizing agent for PdNPs. Formation of PdNPs was preliminarily confirmed by UV–visible and mechanism of formation was proposed from Fourier transform infrared spectroscopy. Transmission electron microscopic images displayed spherical PdNPs with an average size of 11 ± 2 nm. Catalytic activity studies revealed that the PdNPs act as an efficient catalyst for the reduction of both cationic (Methylene Blue) and anionic (Congo red) dye pollutants. Moreover, the PdNPs can be recovered and reused for five cycles without a significant loss in their catalytic activity.

Primary Amine-Functionalized Mesoporous Phenolic Resin-Supported Palladium Nanoparticles as an Effective and Stable Catalyst for Water-Medium Suzuki-Miyaura Coupling Reactions.

Metal nanoparticles have been recognized and widely explored as unique catalysts for carbon-carbon coupling reactions. However, due to their extreme tendency to agglomeration, the generation and stabilization of metal nanoparticles in a porous matrix is an important research field. Herein, novel mesoporous phenolic resin-supported palladium nanoparticles (Pd@NH2-MPRNs) were prepared via direct anionic exchange followed by gentle reduction by using primary amine-functionalized ordered mesoporous phenolic resin as the support. The obtained Pd@NH2-MPRN material still possessed large surface area and ordered two-dimensional hexagonal mesoporous structure. Meanwhile, uniform and well-dispersed palladium nanoparticles were formed in the mesoporous channels, which could be attributed to an efficient complexation and stabilization effect derived from the primary amine groups. As a result, it can promote Suzuki coupling of less activated aromatic bromides to various biaryls in water with high conversion and selectivity. This excellent performance was attributed to small particle sizes, ordered mesopores, and a hydrophobic pore surface, which resulted in the decreased diffusion limitation and the increased active site accessibility. It is noted that it is competitive with the best palladium catalysts known for water-medium Suzuki coupling reaction, and it can be reused at least seven times without significant reduction in the catalytic efficiency, showing a good recyclability. Therefore, this work provides a new potential platform for designing and fabricating robust ordered mesoporous-polymer-supported metal nanoparticles for various catalytic applications.

Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions

Abstract Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (

Metal organic framework derived nitrogen-doped carbon anchored palladium nanoparticles for ambient temperature formic acid decomposition

Well-dispersed palladium nanoparticles (NPs) anchored on a porous N-doped carbon is prepared by wet chemical method, using metal organic frameworks (ZIF-8) as a precursor to derive the porous N-doped carbon support. Benefitting from the N-doping and the porous structure of the carbon materials, the final Pd NPs are in high dispersion and exhibit reduced particle sizes, with electronic structure and chemical status tuned to favor the formic acid decomposition (FAD). The prepared Pd/CZIF-8-950 catalysts show enhanced catalytic performance and selectivity for FAD, the turnover of frequency (TOF) and the mass activity up to 1166 h−1 and 11.01 mol H2 g−1pd h−1 were obtained at 30 °C. This work provides an effective and easy way for synthesis the Pd-based catalyst, which has enormous application prospects for the next generation hydrogen energy preparation and storage.

Microwave-assisted synthesis of palladium nanoparticles supported on copper oxide in aqueous medium as an efficient catalyst for Suzuki cross-coupling reaction

We report here a reliable green method for the synthesis of palladium nanoparticles supported on copper oxide as a highly active and efficient catalyst for Suzuki cross-coupling reaction. The experimental synthetic approach is based on microwave-assisted chemical reduction of an aqueous mixture of palladium and copper salt simultaneously using hydrazine hydrate as reducing agent. The catalyst was fully characterized using various techniques showing well-dispersed palladium nanoparticles. The catalytic activity and recyclability of the prepared catalyst were experimentally explored in the ligand-free Suzuki cross-coupling reaction with a diverse series of functionalized substrates. The synthesized Pd/CuO catalyst shows many advantages beside its high catalytic efficiency such as the recyclability of up to five times with negligible loss of catalytic activity, short reaction times, use of environmentally benign solvent systems, and mild reaction conditions.

Pd-nanoparticle-decorated peanut-shaped BiVO4 with improved visible light-driven photocatalytic activity comparable to that of TiO2 under UV light

Abstract Porous, peanut-shaped BiVO 4 was prepared and further decorated with palladium nanoparticles on its surface using a photodeposition approach. The well-dispersed palladium nanoparticles were found to suppress photogenerated charge carriers, and may also improve the capacity of BiVO 4 to harvest visible light photons due to a local surface plasmon resonance effect. The prepared Pd–BiVO 4 composites exhibited excellent photocatalytic activity in the degradation of phenol under visible light irradiation. This performance rivaled that of TiO 2 under UV light. However, the active oxidants in Pd–BiVO 4 and TiO 2 processes are different, with photogenerated holes in BiVO 4 photocatalysis and OH radicals in TiO 2 photocatalysis. Furthermore, different mechanisms and different pathways for the degradation of phenol under the effects of different oxidants were proposed. This work not only opens up new possibilities for the efficient removal of phenolic compounds in wastewater via visible-light-driven photocatalysis in the presence of a Pd–BiVO 4 composite, but also suggests that OH radicals may not be the most important oxidants in all photocatalysis processes.

Well-dispersed palladium nanoparticles on nickel- phosphorus nanosheets as efficient three-dimensional platform for superior catalytic glucose electro-oxidation and non-enzymatic sensing

In this work, we report a novel well-dispersed palladium nanoparticles (PdNPs)/nickel-phosphorus nanosheets (Ni-P NSs) synthesized by combination of red phosphorous phosphorization and simple electrodeposition technique. The obtained PdNPs/Ni-P nanosheets framework with large electrochemical active surface would not only exhibit much superior electrocatalytic activity (180.5±3.07mAcm−2) toward glucose oxidation reaction, but also represent a wide linear range (2μM−4.65mM) and high sensitive detection of glucose (242.5±3.28μAmM−1cm−2) as non-enzymatic glucose sensor. The three- dimensional (3D) PdNPs/Ni-P nanosheets have a promising prospect as a novel kind of highly active nanocatalyst and non-enzymatic electrochemical sensor.

Well-dispersed Palladium Nanoparticles Catalysts Prepared by Wood Nanomaterials for Suzuki Coupling Reaction

Well-dispersed Palladium Nanoparticles Catalysts Prepared by Wood Nanomaterials for Suzuki Coupling Reaction

Well-dispersed palladium nanoparticles on three-dimensional hollow N-doped graphene frameworks for enhancement of methanol electro-oxidation

In this work, palladium (Pd) nanoparticles/three-dimensional hollow N-doped graphene frameworks (HNGF) hybrid catalysts were fabricated by using amine-functionalized poly (glycidyl methacrylate) microspheres-templated HNGF as supporting materials for Pd nanoparticles (NPs). The results demonstrate that the Pd NPs with average sizes of ~5.5nm can be well dispersed on the surfaces of HNGF with internal circular holes of ~400nm. The Pd/HNGF catalysts exhibit high electrocatalytic activity and durability toward methanol electro-oxidation in alkaline medium, compared to Pd/graphene and Pd/carbon.

Palladium nanoparticles stabilised by cinchona-based alkaloids in glycerol: efficient catalysts for surface assisted processes

Cinchona-based alkaloids led to well-dispersed palladium nanoparticles in neat glycerol, leading to efficient eco-friendly catalytic phases in hydrogenations and hydrodehalogenations.

Palladium nanoparticles supported on amine-functionalized SiO2 for the catalytic hexavalent chromium reduction

Hexavalent chromium (Cr(VI)) is commonly identified acutely toxic, a proven mutagen and carcinogen heavy metal pollutant in the aquatic environment, whereas Cr(III) is believed to be an essential element. In the present study, we show that palladium(0) nanoparticles supported on 3-aminopropyltriethoxysilane (APTS) functionalized silica (Pd@SiO2–NH2) effectively catalyze the reduction of Cr(VI) to Cr(III) by using formic acid (HCOOH) as reducing agent under mild conditions (at room temperature under air). Pd@SiO2–NH2 catalyst was reproducibly prepared by deposition–reduction technique and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV–vis, XPS, BFTEM, HRTEM and TEM-EDX techniques. The sum of their results is indicative of the formation of well-dispersed palladium(0) nanoparticles (dmean=3.7nm) on the surface of APTS-functionalized SiO2. The catalytic performance of the resulting palladium(0) nanoparticles in terms of activity and stability was evaluated by the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid as a reducing agent. Our results reveal that Pd@SiO2–NH2 catalyst displays unprecedented activity (TOF=258mol Cr2O72−/molPdmin) and reusability (<85% at 5th reuse) for the reduction of Cr(VI) to Cr(III) at room temperature. The present study reported here also includes the compilation of wealthy kinetic data for Pd@SiO2–NH2 catalyzed the reduction of Cr(VI) to Cr(III) in aqueous formic acid (HCOOH)–sodium formate (HCOONa) solution depending on substrate [Cr2O72−], catalyst [Pd@SiO2–NH2], surface grafted amine [APTS], formic acid [HCOOH], sodium formate [HCOONa] concentrations, temperature and type of support material (Al2O3, C, unmodified SiO2) to understand the nature of the catalytic reaction and determine the rate expression and activation parameters.

Facile and green cinchonidine-assisted synthesis of ultrafine and well-dispersed palladium nanoparticles supported on activated carbon with high catalytic performance

We report the facile and green synthesis of activated carbon-supported palladium (Pd/AC) containing homogeneously dispersed Pd nanoparticles (Pd NPs) by using eco-friendly and naturally available cinchonidine (CD) as the capping agent.

Selective Hydrogenation of Biomass-Based 5-Hydroxymethylfurfural over Catalyst of Palladium Immobilized on Amine-Functionalized Metal–Organic Frameworks

A catalyst of palladium [Pd/MIL-101(Al)-NH2] supported on amine-functionalized Metal–Organic Frameworks (MOFs) allows selective hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethyl-tetrahydrofuran (DHMTHF) with 2,5-dihydroxymethylfuran (DHMF) as an observed “intermediate”. The Pd/MIL-101(Al)-NH2 was prepared by using a direct anionic exchange approach and subsequent gentle reduction. The presence of free amine moieties in the frameworks of MIL-101(Al)-NH2 is suggested to play a key role on the formation of uniform and well-dispersed palladium nanoparticles on the support. The adsorption experiments reveal that the amine-functionalized MOF supports show preferential adsorption to hydrogenation intermediate DHMF than in the case of reactant HMF owing to an enhanced hydrophilic nature of DHMF as well as improved hydrogen bonding interactions between DHMF and the MOF support, which promotes a further hydrogenation of DHMF to DHMTHF upon the in situ formation of DHMF over Pd/MIL-...

Facile Fabrication of Palladium Nanoparticles Immobilized on the Water-Stable Polyvinyl Alcohol/Polyehyleneimine Nanofibers Via In-Situ Reduction and Their High Electrochemical Activity

A facile strategy for the fabrication of electrochemical biosensors by immobilizing well-dispersed palladium nanoparticles (PdNPs) on the water-stable polyvinyl alcohol/polyethyleneimine (PVA/PEI) nanofibers through the combination of electrospinning technique and the process of in-situ reduction has been demonstrated. The synthesized PdNPs/(PVA/PEI) nanocomposites were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The experimental results confirmed that the PdNPs immobilized on the electrospun PVA/PEI nanofibers with an average diameter of 3.4 nm were well-dispersed, which could be ascribed to the complexation between Pd(II) and the free amine groups of PEI. Further investigations suggested that the PdNPs/(PVA/PEI) nanocomposites with well-separated PdNPs and large surface area exhibited high performance as electrochemical biosensors to detect hydrogen peroxide (H2O2).

Graphene-supported small-sized palladium nanoparticles made by facile photochemical approaches

To achieve small-sized and well-dispersed palladium (Pd) nanoparticles, we make use of effective photochemical approaches to synthesis of clean Pd nanoparticles on the surface of graphene at room temperature. By modulating the photochemical reaction conditions, the size and dispersion of graphene–Pd composites can be well controlled, where PdCl42− and graphene oxide (GO) are the reaction precursors, Hantzsch 1,4-dihydropyridine (HEH) is used as an electron donor and an amine-type ligand to stabilize small Pd nanoparticles on the surface of graphene. As a result, the easy and effective photochemical approaches to the graphene–Pd composites with well-dispersed, small-sized Pd nanoparticles and highly conductive reduced GO, are established. Good to excellent yields have also been achieved with the graphene-supported Pd nanoparticles catalysts for the Suzuki coupling reaction.

Cross-coupling reaction between arylboronic acids and carboranyl iodides catalyzed by graphene oxide (GO)-supported Pd(0) recyclable nanoparticles for the synthesis of carboranylaryl ketones

Well-dispersed palladium(0) nanoparticles with small and narrow size distributions were synthesized conveniently on a graphene oxide (GO) surface. The GO-supported nano-Pd(0) was found to be a highly efficient and recyclable catalyst for the carbonylative cross-coupling reaction between arylboronic acids and aryl and carboranyl iodides, respectively. Benzophenone and a series of carboranylaryl ketones, 1-R-2-[C(=O)Ar]-1,2-C2B10H10 (R = H, Me, Ph; Ar = C6H5, C6H4-4-OMe and C6H4-4-F), were synthesized and fully characterized. The catalyst was recyclable at least three times with sustained activity.

In situ formation of well-dispersed palladium nanoparticles immobilized in imidazolium-based organic ionic polymers.

A new strategy for in situ generation of well-dispersed palladium nanoparticles (NPs) immobilized in imidazolium-based organic ionic polymers was presented. Without extra addition of palladium species, the as-synthesized ionic polymers showed excellent catalytic activity and good reusability in the hydrogenation of nitroarenes.

A facile approach to preparing palladium nanoparticles-embedded polyvinylpyrrolidone (PVP) heterogeneous hybrid nanofibers mats by electrospinning

Well-dispersed palladium nanoparticles (Pd NPs) were prepared under the condition that trisodium citrate was the reduction agent and polyvinylpyrrolidone (PVP) was the stabilizing agent via sol-gel process. By making good use of the advanced electrospinning technology we obtained Pd NPs/PVP composite nanofibers films. Optical properties were examined by UV-visible absorbance spectra (UV-vis) and Fourier transform infrared spectroscopy (FTIR). The morphology and distribution of Pd NPs in/on PVP matrix were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that Pd NPs presented as spherical spots and distributed in/on PVP nanofibers uniformly; their diameter was 4–10 nm and decreased with the increase of PVP. The as-prepared Pd NPs/PVP hybrid mats possess catalytic activity, stability and reusability, as verified by performance in Heck reaction.