Bimetallic PdAg Nanoparticles Research Articles

Preparation and characterization of Ag-Pd bimetallic nano-catalysts in thermosensitive microgel nano-reactor.

Thermosensitive microgels consisting of a solid core of polystyrene and a shell of cross-linked poly(N-isopropylacrylamide) (PNIPA) were synthesized as nano-reactors, in which Ag–Pd bimetallic nanoparticles were prepared through simultaneous in situ reduction reaction. The spatial distribution of metallic nanoparticles in the microgels was analyzed by small angle X-ray scattering (SAXS) and the results indicated that metal nanoparticles were mainly located in the inner layer of microgels. The catalytic activity of Ag–Pd bimetallic nanoparticles was investigated using the reduction of p-nitrophenol to p-aminophenol by NaBH4 as model reaction. The data demonstrated that Ag–Pd bimetallic nanoparticles showed enhanced catalytic activity compared to each monometallic nanoparticle alone and their catalytic activity was controllable by temperature due to the volume transition of PNIPA microgels.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Highly efficient hydrogen release from formic acid using a graphitic carbon nitride-supported AgPd nanoparticle catalyst

Bimetallic AgPd nanoparticles with various molar ratios immobilized on graphitic carbon nitride (g-C3N4) were successfully synthesized via a facile co-reduction approach. The powder XRD, XPS, TEM, EDX, ICP-AES and BET were employed to characterize the structure, size, composition and loading metal electronic states of the AgPd/g-C3N4 catalysts. The catalytic property of as-prepared catalysts for the dehydrogenation of formic acid (FA) with sodium formate (SF) as the additive was investigated. The performance of these catalysts, as indicated by the turnover frequency (TOF), depended on the composition of the prepared catalysts. Among all the AgPd/g-C3N4 catalysts tested, Ag9Pd91/g-C3N4 was found to be an exceedingly high activity for decomposing FA into H2 with TOF up to 480h−1 at 323K. The prepared catalyst is thus a potential candidate for triggering the widespread use of FA for H2 storage.

Sonochemical Synthesis of PdAg/RGO Nanocomposite as an Efficient Electrocatalyst for Both Ethanol Oxidation and Oxygen Reduction Reaction with High CO Tolerance

Controlled size of nanoparticles and rational tuning of the composition could precisely and effectively change the catalytic properties of Pd-based materials, enhancing the electrocatalytic performance and stability. In this article, we reported a rapid and facile synthesis of reduced graphene oxide (RGO) nanosheet-supported alloys of bimetallic PdAg nanoparticles, which were directly prepared by using simultaneous ultrasonic probe irradiation method. The as-synthesized alloys of nanoparticles exhibit excellent electrocatalytic activities for ethanol oxidation and oxygen reduction reaction (ORR) in alkaline medium, including high mass (3138 mA mg−1 Pd) and specific (1.26 mA cm−2) activity on the basis of Pd mass in ethanol oxidation reaction, high electron transferred number (3.94), larger kinetic current density (5.05 mA cm−2), excellent CO tolerance, and long-term stability and durability. The physicochemical and electrochemical characterization of as-prepared electrocatalyst materials was studied by using various tools, such as FE-SEM, HR-TEM, XRD, XPS, FT-IR, CV, CA, EIS, CO-stripping, and LSV-RDE. The developed electrocatalyst is expected to open up a novel class of anode and cathode materials with excellent durability and stability for direct ethanol fuel cell.

Carbon nanotube supported PdAg nanoparticles for electrocatalytic oxidation of glycerol in anion exchange membrane fuel cells

Electro-oxidation of alcohol is the key reaction occurring at the anode of a direct alcohol fuel cell (DAFC), in which both reaction kinetics (rate) and selectivity (to deep oxidation products) need improvement to obtain higher power density and fuel utilization for a more efficient DAFC. We recently found that a PdAg bimetallic nanoparticle catalyst is more efficient than Pd for alcohol oxidation: Pd can facilitate deprotonation of alcohol in a base electrolyte, while Ag can promote intermediate aldehyde oxidation and cleavage of CC bond of C3 species to C2 species. Therefore, a combination of the two active sites (Pd and Ag) with two different functions, can simultaneously improve the reaction rates and deeper oxidation products of alcohols (Applied Catalysis B, 2016, 199, 494). In this continuing work, Pd, Ag mono, and bimetallic nanoparticles supported on carbon nanotubes (Ag/CNT, Pd/CNT, Pd1Ag1/CNT, and Pd1Ag3/CNT) were prepared using an aqueous-phase reduction method; they served as working catalysts for studying electrocatalytic oxidation of glycerol in an anion-exchange membrane-based direct glycerol fuel cell. Combined XRD, TEM, and HAADF-STEM analyses performed to fully characterize as-prepared catalysts suggested that they have small particle sizes: 2.0nm for Pd/CNT, 2.3nm for PdAg/CNT, 2.4nm for PdAg3/CNT, and 13.9nm for Ag/CNT. XPS further shows that alloying with Ag results in more metal state Pd presented on the surface, and this may be related to their higher direct glycerol fuel cell (DGFC) performances. Single DGFC performance and product analysis results show that PdAg bimetallic nanoparticles can not only improve the glycerol reaction rate so that higher power output can be achieved, but also facilitate deep oxidation of glycerol so that a higher faradaic efficiency and fuel utilization can be achieved along with optimal reaction conditions (increased base-to-fuel ratio). Half-cell electrocatalytic activity measurement and single fuel cell product analysis of different glycerol oxidation intermediates, including C3: glycerate, tartronate, mesoxalate, and lactate; C2: glycolate and oxalate, over PdAg/CNT catalyst was further conducted and produced deeper insight into the synergistic effects and reaction pathways of bimetallic PdAg catalysts in glycerol electrocatalytic oxidation.

Bimetallic AgPd Nanoparticles Immobilized on Amine‐Functionalized SBA‐15 as Efficient Catalysts for Hydrogen Generation from Formic Acid

AbstractHCOOH (FA) is considered as a potential hydrogen‐storage material. The chemically stored hydrogen in FA can be catalytically released even at room temperature, which can be utilized by polymer electrolyte membrane fuel cells (PEMFCs). However, in order to make FA a feasible hydrogen‐storage medium, it is necessary to find catalysts with superior performance that enable it to produce hydrogen under moderate conditions. Herein, for the first time to our knowledge, we report amine‐functionalized SBA‐15 (SBA‐15‐Amine)‐supported bimetallic AgPd nanoparticles with various molar ratios through a facile co‐reduction method for serve as a catalyst for the dehydrogenation reaction of FA. As indicated by the turnover frequency (TOF), the performance of these catalysts depended on their composition. Among all the prepared AgPd/SBA‐15‐Amine catalysts, Ag1Pd9/SBA‐15‐Amine exhibited exceedingly high activity for the dehydrogenation of FA to yield high‐quality H2 at 323 K, with a maximum TOF of 964 h−1 and 100 % selectivity. It is revealed that the catalyst exhibits stable catalytic performance after multiple usage cycles. Therefore, the catalyst we developed can be a potential candidate for prompting the widespread utilization of FA as a hydrogen‐storage material.

Catalytic Oxidation of 1,2-Propanediol to Lactic Acid with O<SUB>2</SUB> Under Atmospheric Pressure Over Pd–Ag Bimetallic Nanoparticles and Reaction Kinetics

Catalytic Oxidation of 1,2-Propanediol to Lactic Acid with O<SUB>2</SUB> Under Atmospheric Pressure Over Pd–Ag Bimetallic Nanoparticles and Reaction Kinetics

Facile Synthesis of PdAgCo Trimetallic Nanoparticles for Formic Acid Electrochemical Oxidation

PdAg bimetallic and PdAgCo trimetallic nanoparticles (NPs) are synthesized by a one-pot method in an organic solvent medium. Our results show that the catalytic activity of PdAgCo/C (1133.249 mA mgPd−1) for formic acid oxidation (FAO) is ca. 2.4 times larger than commercial Pd/C (483.563 mA mgPd−1) and 1.7 times larger than PdAg/C (680.741 mA mgPd−1). This study indicates that Co doping in PdAg bimetallic NPs can significantly improve its FAO activity. It is expected that the as-synthesized PdAgCo trimetallic NPs could be used as high-performance catalysts for direct formic acid fuel cells (DFAFCs).

Efficient hydrogen generation from formic acid using AgPd nanoparticles immobilized on carbon nitride-functionalized SBA-15

Bimetallic AgPd nanoparticles were successfully immobilized on graphitic carbon nitride (g-C3N4) functionalized SBA-15 for the first time by a facile co-reduction method.

Visible light mediated upgrading of biomass to biofuel

Heterogenized bimetallic Ag–Pd nanoparticles on graphitic carbon nitride (AgPd@g-C3N4) promote upgrading of biofuel via hydrodeoxygenation of vanillin under visible light irradiation using formic acid as a hydrogen source.

The AgcorePdshell bimetallic nanoparticles: simple biological synthesis and characterization

In this work and for the first time, bimetallic Ag–Pd nanoparticles equipped with a core–shell structure were prepared biologically by employing a galvanic displacement reaction in which the added PdCl2 reacts with an Ag nanotemplate containing an adsorbed soaproot (Acanthe phylum bracteatum) extract. Four samples with different Ag/Pd molar ratios of 100:2, 100:5, 100:10 and 100:15 were prepared to synthesize the bimetallic nanoparticles with a core–shell structure. The bimetallic Ag–Pd nanoparticles were characterized using UV–visible spectroscopy (UV–Vis), X-ray diffraction (XRD), scanning electron microscopy with an energy-dispersive X-ray spectroscopy (SEM–EDX), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The results from UV–Vis revealed an optimal molar ratio of 100:15 for Ag/Pd, which is appropriate to prepare bimetallic Ag–Pd nanoparticles with the core–shell structure. The results of FTIR and XRD confirmed the pure bimetallic Ag–Pd nanoparticles formation. The images prepared by TEM depicted spherical and uniformly shaped nanoparticles without any agglomeration and a particle size of 15 nm.

Structural Evolution of Ag–Pd Bimetallic Nanoparticles through Controlled Galvanic Replacement: Effects of Mild Reducing Agents

Galvanic replacement provides a simple but versatile way of converting less noble metallic solid nanoparticles into structurally more complex multimetallic hollow nanostructures composed of more noble metals. In contrast to the well-studied Ag–Au bimetallic hollow nanostructures, limited success has been achieved on the geometry control over Ag–Pd bimetallic nanoparticles through galvanic replacement reactions. Here we demonstrate that the capability of geometry control over Ag–Pd bimetallic hollow nanostructures through nanoscale galvanic replacement can be greatly enhanced by the use of appropriate mild reducing agents, such as ascorbic acid and formaldehyde. With the aid of mild reducing agents, we have been able to fine-tailor the compositions, interior architectures, and surface morphologies of Ag–Pd bimetallic hollow nanoparticles with increased structural complexity through surface ligand-free galvanic replacement processes at room temperature. This reducing agent-mediated galvanic replacement prov...

Synergistic catalysis of AgPd@ZIF-8 on dehydrogenation of formic acid

Highly dispersed bimetallic AgPd nanoparticles with different composition have been successfully deposited on the metal-organic frameworks (ZIF-8) by using a simple liquid impregnation method. The resultant catalysts are composition dependent toward dehydrogenation of formic acid, while Ag18Pd82@ZIF-8 exhibits exceedingly high catalytic activity, with the turnover frequency (TOF) value of 580h−1, and 100% hydrogen selectivity at 80°C.

Study of Ag–Pd bimetallic nanoparticles modified glassy carbon electrode for detection of L-cysteine

Ag–Pd bimetallic nanoparticles (Ag–Pd BNPs) as an enhanced sensing material with improved electronic transmission rates in the electrochemical sensing of L-cysteine (L-cys) has been reported. The morphology of Ag–Pd BNPs was characterized with X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Oxidation of L-cys on Ag–Pd BNPs is investigated in detail by discussing the effect of the structure and from the electrocatalytic oxidation of L-cys. We found that the Ag–Pd BNPs exhibited high electrocatalytic activity towards L-cys oxidation in neutral condition and could be used for the development of nonenzymatic L-cys sensor. Based on the efficient catalytic ability of Ag–Pd BNPs, the fabricated biosensor exhibited a wide linear range of responses to the L-cys with the concentration detection limit of nearly down to 2mM with fast response time.

Fast synthesis of Ag–Pd@reduced graphene oxide bimetallic nanoparticles and their applications as carbon–carbon coupling catalysts

Ultrafine Ag–Pd bimetallic nanoparticles homogeneously distributed on reduced graphene oxide (rGO) were prepared by redox reactions between Pd2+, Ag+ and GO. This method is simple, and the use of rGO as a support facilitated the separation and reuse of the Ag–Pd@rGO catalyst. The Ag–Pd@rGO bimetallic nanoparticles were characterized by ultraviolet-visible spectroscopy, Raman spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The microstructure of the Ag–Pd@rGO was investigated with scanning electron microscopy and transmission electron microscopy. The Ag–Pd@rGO catalyst exhibited high catalytic activities in the Suzuki-Miyaura carbon coupling reaction and the Sonogashira carbon coupling (SCC) reaction. These reactions used mild, efficient, ligand-free and heterogeneous conditions. Interestingly, the presence or absence of oxygen in the SCC catalytic system resulted in two different products, in which oxygen can be used as “switch” to control different products.

Mesoporous Ti(0.5)Cr(0.5)N supported PdAg nanoalloy as highly active and stable catalysts for the electro-oxidation of formic acid and methanol.

We report a robust noncarbon Ti0.5Cr0.5N support synthesized by an efficient solid-solid phase separation method. This ternary nitride exhibits highly porous, sintered, and random network structure with a crystallite size of 20-40 nm, resulting in a high specific surface area. It is not only kinetically stable in both acid and alkaline media, but also electrochemically stable in the potential range of fuel cell operation. Two typical anode reactions, formic acid oxidation in acid media and methanol oxidation in alkaline media, are employed to investigate the possibility of Ti0.5Cr0.5N as an alternative to carbon. Bimetallic PdAg nanoparticles (∼4 nm) act as anode catalysts for the two anode reactions. PdAg/Ti0.5Cr0.5N exhibits much higher mass activity and durability for the two reactions than PdAg/C and Pd/C catalyst, suggesting that mesoporous Ti0.5Cr0.5N is a very promising support in both acid and alkaline media.

Spectroscopic Characterization of Stability and Interaction of Pd-Ag Complexes

Colloidal metal nanoparticles are of great interest because of their use as catalysts, photocatalysts, adsorbents, and sensors as well as their application in optical, electronic, and magnetic devices. Supported bimetallic systems represent a large part of heterogeneous catalysts which have been used in various reactions important in the chemical, petrochemical, and oil industry. Pd-Ag bimetallic nanocatalysts have become vitally important in some of the petrochemical industry’s processes like hydrogenation of C2–C5 olefins. A heat-treatment method for the preparation of well-stable Pd-Ag complexes is demonstrated using water, concentrated HCl and concentrated nitric acid as media. The stability and interaction of Pd-Ag complexes were characterized by UV-vis absorption spectroscopy. Pd-Ag bimetallic nanoparticles of spherical cubic and octahedral shape in the range of average particle size of 20–60 nm have been prepared and characterized by transmission electron microscopy (TEM).

Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd80Ag20 nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system.

Metal Nanoparticle Catalysts for Oxidation of Propene with Molecular Oxygen

Abstract AgPd bimetallic nanoparticles were prepared by the reduction of the salts of Ag+ and Pd2+ ions with NaBH4 in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) in an aqueous solution placed in an ice bath and were characterized with a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray spectroscope (EDS). The prepared AgPd bimetallic nanoparticles had higher catalytic activity and selectivity for aerobic oxidation of propene to propene oxide than did conventional Pd salts and Pd and Ag monometallic nanoparticles.

Bimetallic Nanoparticles: Kinetic Control Matters

Morphologies à la carte: a kinetic control strategy has been utilized to fabricate bimetallic nanoparticles. Using cubic Pd nanocrystals as seeds and a syringe pump that enables precise control over precursor injection rate, it is possible to synthesize Pd-Ag bimetallic nanoparticles with tailored shapes and tunable localized surface plasmon resonances.