Dispersed Palladium Nanoparticles Research Articles

One-step fabrication of a highly dispersed palladium nanoparticle-decorated reduced graphene oxide electrocatalyst for methanol electro-oxidation in acidic media

Reduced graphene oxide (RGO) was successfully decorated with homogeneous highly dispersed palladium nanoparticles (PdNPs) by a novel single-step hydrothermal-assisted formic acid reduction reaction without the use of any surfactants. The structure, surface morphology, and elemental composition of the as-prepared PdNP-RGO electrocatalyst were extensively characterized. The PdNP-RGO electrocatalyst demonstrated outstanding electrocatalytic activity (8.65 mA/cm2) toward the methanol oxidation reaction (MOR) in an acidic medium that is 1.4 times higher than PdNP-decorated Vulcan XC72 (6.2 mA/cm2) and also comparable with that of Pd-based electrocatalysts in alkaline media from the previous reports. Furthermore, the as-prepared PdNP-RGO electrocatalyst also shows remarkable stability performance for the MOR in an acidic medium and thus offer new insights into the processing method of an outstanding electrocatalyst at the anode electrode in the direct methanol fuel cell with reasonable cost, clean and facile synthesis approach.

Palladium nanoparticles dispersed on functionalized macadamia nutshell biomass for formic acid-mediated removal of chromium(VI) from aqueous solution

Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction analysis confirmed the formation of Pd on the modified MNS surface and suggested an estimated crystallite size of 5.0 nm. The supported nanoparticles exhibited catalytic activity in formic acid-mediated Cr(VI) reduction and showed promising stability with consecutive reuse. These findings set the stage for advanced studies into performance optimization.

Effect of the distribution and dispersion of palladium nanoparticles on the reducibility and performance of Pd/Al2O3 catalyst in liquid-phase hydrogenation of olefins

A series of Pd/γ-Al2O3 catalysts were prepared by wet impregnation method at different pH and time. The effect of metal distribution and dispersion on the catalyst reducibility in liquid-phase hydrogenation of olefins was studied. The samples were characterized by BET, XRD, ICP, FESEM, CO-chemisorption and H2-TPR techniques. Liquid-phase hydrogenation reaction was carried out in a three-phase trickle bed reactor to evaluate the performance of the catalyst samples. The best catalyst performance was attributed to a combination of its desirable characteristics, that is, high reducibility at lower temperatures, high Pd dispersion and an egg-shell Pd distribution which increase the accessibility of the reactants to Pd active sites in this diffusion-limited reaction.

Effective hydrogen gas sensor based on palladium nanoparticles dispersed on graphene sheets by spin coating technique

Abstract A room-temperature hydrogen gas (H2) sensor was successfully fabricated by dispersion of palladium nanoparticles (Pd NPs) on graphene sheets (GRs) (hereafter referred to as “Pd NPs/GRs”). GRs and Pd NPs were synthesized by chemical vapor deposition technique and by polyol process, respectively. A colloidal solution of Pd NPs with an average diameter of 11 nm was then dispersed onto the GRs by spin coating technique. The density of dispersed Pd NPs on GRs was controlled by varying the volume of the dispersed solution within the range of 50 – 150 μL. The fabricated Pd NPs/GRs sensors exhibited a high sensitivity for H2 gas with a concentration of 1500 – 6000 ppm at room temperature. Upon H2 exposure, the Pd NPs/GRs sensors showed an increase in electrical resistance, which could easily be measured. The relationship between sensor response and H2 concentration is in correspondence with the Langmuir adsorption model. The H2 detection limit is estimated to be 1 ppm. The results demonstrate that the Pd NPs/GRs sensor is an easily fabricated, but very effective means for room-temperature detection of H2at ppm level.

Fabrication and characterization of ternary sepiolite/g-C3N4/Pd composites for improvement of photocatalytic degradation of ciprofloxacin under visible light irradiation

The development of high-quality photocatalytic materials for the degradation of organic pollutants under visible light irradiation is a vital field of research. In the present study, a composite of natural sepiolite clay and synthetic graphitic carbon nitride (CN) mixed with dispersed palladium nanoparticles was developed for the efficient photocatalytic degradation of ciprofloxacin (CIP) under visible light irradiation. The sepiolite, CN, and composite materials were characterized by several techniques. The sepiolite/CN composite (SC30%) displayed superior activity than pristine sepiolite and CN, resulted from the generation of new electron trap states in the interfacial contract between sepiolite and CN to suppress the charge recombination of CN. Furthermore, the well-dispersed of 1 wt% Pd-nanoparticles in the SC30% composite collectively enhanced CIP degradation by avoiding the recombination of photogenerated electrons and holes. Additionally, the electron trap states on the surface of all samples were studied using novel reversed double-beam photoacoustic spectroscopy to understand electron transfer in the composites related to the photocatalytic degradation mechanism of CIP. The developed sepiolite/CN/Pd(0) composite can act as a potential catalyst for the degradation of organic pollutants in wastewater under visible light irradiation.

Preparation of Carbon-Supported Highly Dispersed Palladium Nanoparticles and Their Performance for Suzuki Reaction

Preparation of Carbon-Supported Highly Dispersed Palladium Nanoparticles and Their Performance for Suzuki Reaction

Palladium Nanocatalysts Encapsulated on Porous Silica @ Magnetic Carbon‐Coated Cobalt Nanoparticles for Sustainable Hydrogenation of Nitroarenes, Alkenes and Alkynes.

AbstractPalladium nanoparticles were impregnated on porous silica shell carbon‐coated cobalt nanoparticles, resulting in a magnetically retrievable material that was evaluated in the catalytic hydrogenation of nitroarenes, alkenes and alkynes. The prepared material was characterized by HR‐XRD, HR‐TEM, elemental mapping EDX, ICP‐OES and XPS analyses, revealing highly dispersed palladium nanoparticles within the porous platform that could account for the high activity observed. Mild reaction conditions, easy retrievability of the catalyst with the aid of an external magnet, recycling in four runs with a total leaching of 19 ppm (1.2 % of the initially employed Pd amount), and high stability makes this material attractive for sustainable and environmentally benign applications.

Immobilizing palladium nanoparticles on boron-oxygen-functionalized carbon nanospheres towards efficient hydrogen generation from formic acid

Carbon nanospheres (XC-72R) were functionalized by boron-oxygen (B-O) through coannealing with boric acid, to which highly dispersed palladium nanoparticles (Pd NPs) (~ 1.7 nm) were immobilized by a wet chemical reduction for the first time. The resultant Pd/OB-C catalyst exhibits significantly improved activity for the dehydrogenation from formic acid (FA) compared to pristine XC-72R supported Pd NPs (Pd/C). Impressively, by adding melamine precursor, the B-O and nitrogen (N)-functionalized product OB-C-N displays an extremely high B content, ca. 34 times higher than OB-C. The Pd/OB-C-N catalyst with an ultrafine Pd particle size of ~ 1.4 nm shows a superb activity, with a turnover frequency (TOF) as high as 5,354 h−1 at 323 K, owing to the uniform ultrafine Pd NPs and the effect from B-O and N functionalities.

Black Phosphorus/Palladium Nanohybrid: Unraveling the Nature of P-Pd Interaction and Application in Selective Hydrogenation.

The burgeoning interest in two-dimensional (2D) black phosphorus (bP) contributes to the expansion of its applications in numerous fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. Electron energy loss spectroscopy–scanning transmission electron microscopy analysis evidences a strong interaction between palladium and P atoms of the bP nanosheets. A quantitative evaluation of this interaction comes from the X-ray absorption spectroscopy measurements that show a very short Pd–P distance of 2.26 Å, proving for the first time the existence of an unprecedented Pd–P coordination bond of a covalent nature. Additionally, the average Pd–P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand toward the surface of the Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring with structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroanilines, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.

Highly Dispersed Palladium Nanoparticles on Carbon-Decorated Porous Nickel Electrode: An Effective Strategy to Boost Direct Ethanol Fuel Cell up to 202 mW cm–2

The low performance and low catalyst utilization of electrodes have been challenging issues for anion-exchange membrane direct liquid fuel cells (AEM DLFCs). Herein, a high-utilization and high-act...

Highly active and stable supported Pd catalysts on ionic liquid-functionalized SBA-15 for Suzuki–Miyaura cross-coupling and transfer hydrogenation reactions

Highly dispersed palladium nanoparticles were synthesized in the presence of immobilized ionic liquid on mesoporous silica SBA-15. PdNPs(2.4 nm)_me-Im@SBA-15 catalyst was prepared by the reduction using NaBH4 as the reducing agent with controlled feed rate and has been investigated as ligand-free catalyst for Suzuki–Miyaura cross-coupling reaction at room temperature in aqueous solution under air. PdNPs catalyst was also prepared in situ from PdCl4_me-Im@SBA-15 during the reaction and demonstrated high activity and stability towards nitrobenzene hydrogenation at high temperature. Both catalysts were reusable at least for four recycle processes without significant loss in activity with simple procedure. The catalysts were characterized by TEM, EXAFS, FTIR and XPS.

Pd nanoparticle supported reduced graphene oxide and its excellent catalytic activity for the Ullmann C-C coupling reaction in a green solvent.

An efficient and easy route to synthesize reduced graphene oxide with well dispersed palladium (Pd) nanoparticles (Pd(0)-RGO) is described. The synthesized materials were fully characterized by different techniques such as: XRD, FTIR, Raman, SEM, and TEM. An average particle size of 7.5 nm for the metal particles was confirmed by TEM analysis. Pd(0)-RGO demonstrated outstanding catalytic activity for Ullmann coupling with 97% yield and good reusability (4 cycles).

Controlled synthesis of modified polyacrylamide grafted nano-sized silica supported Pd nanoparticles via RAFT polymerization through “grafting to” approach: application to the Heck reaction

Polyacrylamide grafted onto silica nanoparticles (nano-SiO2-g-PAAm) was prepared through “grafting to” approach via controlled reversible addition-fragmentation chain transfer (RAFT) polymerization system with defined molecular weight and graft density. Modification of the nano-SiO2-g-PAAm with ethanolamine and subsequent reaction with chlorodiphenylphosphine (ClPPh2) was produced polymer-grafted silica with phosphinite functionality which was converted to Pd catalyst through the reaction with Pd(OAc)2. The catalyst was characterized using ICP, FT-IR, TGA, SEM, and DLS methods properly. Dispersion of palladium nanoparticles (PdNPs) in the polymer matrix (10–15-nm range) and existence of Pd in zero oxidation state was verified by TEM and XRD techniques. The catalyst demonstrated activity in the Mizoroki-Heck cross-coupling reaction of varied iodoarenes including electron poor, electron rich, and ortho substituted and heterocycles with olefins efficiently. Reusing of the Pd catalyst was performed at least five times in repeating runs without considerable palladium leaching and change of the catalyst function and structure.

Robust Zirconium Phosphate–Phosphonate Nanosheets Containing Palladium Nanoparticles as Efficient Catalyst for Alkynes and Nitroarenes Hydrogenation Reactions

Thin nanosheets based on layered zirconium mixed phosphate–phosphonate of formula Zr2(PO4)[(PO3CH2)2NCH2COOH]2·H2O were obtained by exfoliation in aqueous solution of propylamine of the pristine crystalline precursor. Highly dispersed palladium nanoparticles, of 2–5 nm average size, were generated using palladium acetate Pd please change as precursor with as Pd source and immobilized on the nanosheet surface. The resulting layered nanohybrids differ in the palladium loading (from 5 to 22% in weight of Pd) and in the amount of propylamine intercalated between the nanosheets. The new 2D material was investigated catalyst in the partial hydrogenation of C≡C bonds and in the selective reduction of nitroarenes, showing very good selectivity at full conversion under room temperature, with pretty constant activity upon recycle. Metal leaching in solution was negligible well no additives nor regeneration steps were needed for repeated use.

Morphology and Size Effect of Ceria Nanostructures on the Catalytic Performances of Pd/CeO2 Catalysts for Methanol Decomposition to Syngas

Palladium is an active catalyst for the decomposition of methanol to syngas, and its chemical activity is largely affected by the interaction with the supporting substrate. Nanostructured cerium oxide can establish strong electronic interactions with finely dispersed palladium nanoparticles (NPs) leading to a substantial enhancement of their catalytic performance. To study this synergistic effect and connect it to structural parameters, we deposited Pd NPs on nanostructured cerium oxide particles exposing mainly the same (100) surface, but with different nanoshape and average dimension, and we have investigated their activity toward the methanol decomposition reaction. A systematic comparison of photoemission measurements taken at every step of the catalytic cycle allowed us to identify the most important factors that control the redox properties of the Pd/CeO2 systems and therefore the overall catalytic activity. Capitalizing on this knowledge it was possible to synthesize synergistic nanocatalysts with ...

Enhanced Catalytic Glycerol Oxidation Activity Enabled by Activated‐Carbon‐Supported Palladium Catalysts Prepared through Atomic Layer Deposition

AbstractThe ability to precisely engineer advanced catalysts for the oxygen reduction reaction (ORR) and glycerol oxidation reaction (GOR) is crucial for the deployment of fuel cells (FCs) and electrolyzers. In this work, we used an atomic layer deposition (ALD) process to prepare highly dispersed palladium nanoparticles (PdNPs) on electro‐activated carbon felt electrodes. The prepared PdNPs were well dispersed and presented diameters of 4–6 nm, corresponding to a mass loading of 96 μgPd cm−2 or 0.9 wt.%. For the GOR, the as‐synthesized nanocatalysts outperformed the commercial Pd/C (20 wt.%) reference by an order of magnitude. The bare electrode also displays distinguished kinetics towards the ORR. The enhanced performance is explained by the good palladium‐carbon interaction and the reduced aggregation and/or detachment of PdNPs. The results uncovered herein provide new strategic routes for the development of advanced electrodes for applications in electrochemical energy conversion.

Cucurbit[6]uril-Stabilized Palladium Nanoparticles as a Highly Active Catalyst for Chemoselective Hydrogenation of Various Reducible Groups in Aqueous Media

Herein, we report the synthesis, characterization, and application of uniformly dispersed palladium nanoparticles supported on cucurbit[6]uril. The 2.56 wt% Pd was loaded on cucurbit[6]uril by impregnation method. Cucurbit[6]uril is a macrocyclic compound in which six glycoluril units are joined with twelve methylene bridges which not only act as support but also helped in stabilizing Pd nanoparticles. The synthesized catalyst was thoroughly characterized by various physicochemical methods. The high resolution transmission electron microscopic analysis revealed the uniform distribution of Pd nanoparticles with average size of ∼3 nm over the cucurbit[6]uril surface. Furthermore, the synthesized catalyst was used for the chemoselective hydrogenation of various reducible (epoxide, olefin, carbonyls, nitrile, azo, imines and nitroarenes) groups with excellent conversion, selectivity (> 99%) and high turnover frequency (up to 2,05,882 h−1) in aqueous and in some cases with water-THF mixture. Also, the catalyst was successfully recycled several times (>10 times) without losing any significant conversion and selectivity. Moreover, the leaching results were confirmed by analyzing reaction mixture by inductively coupled plasma atomic emission spectroscopy. Furthermore, the kinetic studies reveal the reaction rate depends on substrate concentration. The reaction mechanism was investigated by studying the reaction through drift FTIR studies.

Biogenic synthesis of palladium nanoparticles and their applications as catalyst and antimicrobial agent.

This paper describes a simple in-situ process of synthesizing highly dispersed palladium nanoparticles (PdNPs) using aqueous leaf extract of GarciniapedunculataRoxb as bio-reductant and starch (0.3%) as bio-stabilizer. The PdNPs are characterized by techniques like FTIR, TEM, SEM-EDX, XRD and XPS analysis. It is worthnoting thatwhen the synthesis of nanoparticles was carried out in absence of starch, agglomeration of particles has been noticed.The starch-assisted PdNPs showed excellent aqueous-phase catalytic activities for three important reactions: the Suzuki-Miyaura cross-coupling reactions of aryl halides (aryl bromides and iodides) with arylboronic acids; selective oxidations of alcohols to corresponding carbonyl compounds; and reduction of toxic Cr(VI) to nontoxic Cr(III). Our catalyst could be reused up to four cycles without much compromising with its activity. Furthermore, the material also demonstrated excellent antimicrobial and anti-biofilm activities against a novel multidrug resistant clinical bacterial isolate Cronobactersakazakii strain AMD04. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PdNPswere found to be 0.06 and 0.12 mM respectively.

Hydrodeoxygenation of water-insoluble bio-oil to alkanes using a highly dispersed Pd\u2013Mo catalyst

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.

Fabrication of Polybenzimidazole/Palladium Nanoparticles Hollow Fiber Membranes for Hydrogen Purification

AbstractA novel scheme to fabricate polybenzimidazole (PBI) hollow fiber membranes with a thin skin loaded with fully dispersed palladium nanoparticles is proposed for the first time. Palladium is added to the membrane during the spinning process in the form of ions that coordinate to the imidazole groups of the polymer. This is attractive for membrane production because agglomeration of nanoparticles is minimized and the high‐cost metal is incorporated in only the selective layer—where it is required. Pd‐containing membranes achieve three orders of magnitude higher H2 permeances and a twofold improvement in H2/CO2 selectivity compared to pure PBI hollow fiber membranes.