Bimetallic PdAg Research Articles

Assembly of Bimetallic PdAg Nanosheets and Their Enhanced Electrocatalytic Activity toward Ethanol Oxidation.

The direct ethanol fuel cells in an alkaline medium have a broad vision of applications because of their large energy density, reasonable power density, and environmentally friendly features. Herein, we present a facile one-step method to synthesize PdAg nanosheet assemblies (NSAs) in a mixed solution of N,N-dimethylformamide and water with the addition of molybdenum hexacarbonyl and cetyltrimethylammonium bromide. Pure Pd NSA shows an irregular shape while PdAg NSAs gradually undergo a process from solid assembly to a hollow structure with the Pd/Ag molar ratio changing from 3:1 to 2:1 to 1:1. The formation of alloy nanosheets in the assemblies combined with the introduction of Ag in the Pd catalyst enhances the catalytic activity toward ethanol electrooxidation from 1524 mA mg-1 of pure Pd NSA to 1866 mA mg-1 of PdAg NSA with a Pd/Ag molar ratio of 2:1. On the basis of the experimental data, compared with pure Pd structures, both the nature of a thin nanosheet of PdAg NSAs and the structural changes in the alloy assemblies play key roles in determining the electrocatalytic activity of these Pd-based catalysts.

Electrosynthesis of Ammonia Using Porous Bimetallic Pd–Ag Nanocatalysts in Liquid- and Gas-Phase Systems

Cost-effective production of ammonia via electrochemical nitrogen reduction reaction (NRR) hinges on N2 electrolysis at high current densities with suitable selectivity and activity. Here, we repor...

Liquid-phase acetylene hydrogenation over Ag-modified Pd/Sibunit catalysts: Effect of Pd to Ag molar ratio

A series of bimetallic Pd–Ag catalysts supported on the carbon material Sibunit was synthesized for selective liquid-phase acetylene hydrogenation. Using XRD and EXAFS it was shown that palladium and silver in the 0.5% Pd–Ag/Sibunit can form bimetallic PdxAg(1−x) nanoparticles with the composition depending on the Pd:Ag ratio. The active component of Pd–Ag(1:0.25)/Sibunit, Pd–Ag(1:1)/Sibunit and Pd–Ag(1:4)/Sibunit is represented by the particles of Pd0.74Ag0.26, Pd0.60Ag0.40 and Pd0.41Ag0.59 nanoalloys, respectively. An increase of the quantity of silver decreases the catalyst activity. The XPS study revealed that this phenomenon is caused by a decrease in the surface concentration of palladium (geometrical effect) and an increase in the degree of palladium electronic modification with silver (electronic effect). The latter exerts a beneficial effect on the reaction selectivity: as the Pd:Ag molar ratio is raised to 1:2, selectivity to ethylene increases to 81% (X > 97%), which exceeds 2.7-fold the selectivity of Pd/Sibunit.

Ag/Pd bimetal nanozyme with enhanced catalytic and photothermal effects for ROS/hyperthermia/chemotherapy triple-modality antitumor therapy

We prepared an Ag/Pd bimetallic nanozyme with the peroxidase-like activity as a nanocarrier to load doxorubicin (DOX). It combines photothermal conversion ability and catalytic production of hydroxyl radicals (HO•) to achieve enhanced antitumor effects. The temperature rise under near-infrared (NIR) laser irradiation was recorded to demonstrate the photothermal conversion ability of the Ag/Pd bimetallic nanoparticles (AgPd NPs). The peroxidase-like activity of the AgPd NPs was visually characterized by a color rendering experiment of TMB. Compared with bare Ag NPs, bimetallic AgPd NPs exhibit better photothermal conversion capability (η = 40.97%) and catalytic ability resulting from alloying with palladium. The antitumor effect was evaluated by cell experiments and tumor-bearing mice experiments, and it was confirmed that AgPd@BSA/DOX has excellent antitumor activity in vitro and in vivo. These results indicate that the AgPd@BSA/DOX can effectively catalyze hydrogen peroxide to generate hydroxyl radicals and induce hyperthermia under the irradiation of the NIR laser while releasing the chemotherapy drug DOX to achieve triple modality treatment. Intrinsic enzymatic activity and photothermal property of AgPd@BSA/DOX can be synergized for efficient antitumor treatment, which provided a novel strategy for cancer therapy.

Facile one-step room temperature synthesis of PdAg nanocatalysts supported on multi-walled carbon nanotubes towards electro-oxidation of methanol and ethanol

Pd nanocatalysts still suffer from poor activity and rapid stability degradation due to incomplete oxidation reaction of methanol and ethanol. Herein, we report the facile synthesis of bimetallic PdAg supported on multi-walled carbon nanotube (MWCNT) nanocatalysts prepared via one-step room temperature chemical reduction strategy without additional of any capping agents towards the electrooxidation of methanol and ethanol in alkaline medium. During the synthesis process, reduction reaction between PdCl2, AgNO3 and NaBH4 led to bimetallic PdAg/MWCNT electrocatalysts. The results revealed that the PdAg NPs are uniformly-dispersed on the surface of MWCNT with a well-defined structure, small particle size (5.5 nm) and high surface active area (117.49 m2gPd−1). XPS results showed a strong charge transfer interaction between Pd and Ag atoms on catalytic surface. Cyclic voltammetry (CVs) results demonstrate that as-obtained PdAg/MWCNT electrocatalysts exhibit higher electrochemical activity and long-term durability for methanol and ethanol oxidation than the Pd/C (JM) electrocatalysts. Moreover, Pd3·5Ag/MWCNT electrocatalyst exhibit higher electrochemical performance in ethanol (3722mA mgPd−1) than methanol (1619.52 mA mgPd−1). This method has shown promising effect as advance strategy for the synthesis of low cost and high-performance Pd-based nanocatalysts, and for large-scale application as well.

Enhancing ORR Performance of Bimetallic PdAg Electrocatalysts by Designing Interactions between Pd and Ag

Precise tuning of the electronic properties of Ag/C using under potentially deposited (UPD) Cu and subsequent galvanic displacement to deposit atomically dispersed loading of Pd resulted in a robus...

Heterogeneous AgPd Alloy Nanocatalyst for Selective Reduction of Aromatic Nitro Compounds Using Formic Acid as Hydrogen Source

A Heterogeneous catalyst developed for selective reduction of nitroarenes to the analogous anilines using formic acid as hydrogen source. This catalytic procedure offers a simplistic path to prepare aromatic amines in good to excellent yields. Especially, even anilines functionalized with other potentially reducible moieties are obtained with high selectivity. Herein, we report convenient and stable bimetallic AgPd nanocatalyst supported on metal organic framework coated with polyaniline. Hydrogenation of nitroarenes gave analogues anilines with excellent yields at 90 °C in 6 h with no use of additives. Catalyst maintained stable performance in five repeated cycles.

Green synthesis of silver and palladium nanocomposites: a study of catalytic activity towards etherification reaction

This work deals with the synthesis of biomolecule-based monometallic Ag and Pd and bimetallic Ag–Pd nanocomposites and their catalytic activity towards etherification reaction.

Porous organic polymer supported PdAg bimetallic catalyst for the hydrodeoxygenation of lignin-derived species

A nitrogen-riched porous organic polymer named as BA-M was synthesized by co-polymerization of benzene and aniline monomers with dimethoxymethane as cross-linker through a simple Friedel-Crafts alkylation reaction. A series of the porous organic polymer supported bimetallic PdAg nanoparticles catalysts were developed for the selective hydrodeoxygenation of lignin-derived species including vanillin, isoeugenol and so on. The remarkable catalytic performance with 100% conversion of vanillin and 100% selectivity to p-creosol were achieved over the Pd9Ag1/BA-M catalyst at mild condition (low hydrogen pressure and temperature). The Pd9Ag1/BA-M catalyst also showed excellent recyclability with the catalytic activity and selectivity being well preserved after six catalytic recycles. The interaction between metal nanoparticles and porous organic polymer support, together with the nitrogen species in porous organic polymer support were primarily responsible for the excellent catalytic performance of bimetallic PdAg catalysts.

Monodispersed silver-palladium nanoparticles for ethanol oxidation reaction achieved by controllable electrochemical synthesis from ionic liquid microemulsions

Alloyed nanoparticles are promising electrocatalysts for electrochemical energy storage and conversion devices. However, syntheses of alloyed nanoparticles with controllable size and stoichiometry remain challenging. In this study, continuous, uniform and monodispersed bimetallic AgPd nanoparticles (NPs) with diameters ∼10 nm are achieved by electrochemical synthesis from quaternary ionic liquid microemulsion (ILM) for use as electrocatalysts for ethanol oxidation reaction (EOR). It is found that the ionic liquid, 1-butyl-3-methyl-imidazolium chloride ([BMIM]Cl), acts not only as a soft template and co-surfactant for the formation of micro-reactors, but also as an electrolyte for enhancing conductivity. The stoichiometry (AgxPdy), size and size distribution of AgPd NPs can be accurately tuned by varying electrolyte composition, electrodeposition conditions, and ionic liquids concentrations. Attributed to the high surface area, optimal stoichiometric ratio, and strong attachment onto substrates without using organic binders, the as-deposited AgxPdy NPs exhibit extraordinary electrocatalytic activity and stability for EOR. It is found that the mass activity of Ag49Pd51 NPs/Pt electrode reaches 3360 mA mg−1 for EOR in 1.0 M ethanol and 1.0 M KOH aqueous solution, which is much higher than commercial Pd/C catalyst (210.5 mA mg−1) and also the highest among state-of-the-art AgPd NPs electrocatalysts reported to date for EOR in alkaline media.

Rational design of thermoresponsive functionalized MCM-41 and their decoration with bimetallic Ag–Pd nanoparticles for catalytic application

Abstract MCM-41 was functionalized with thermoresponsive poly (N-isopropyl acrylamide) (p-NIPAM) by free radical polymerization. The surface of the p-NIPAM-coated on MCM-41 (MCM-41/p-NIPAM) nanocatalyst was decorated with bimetallic Ag–Pd nanoparticles for catalytic applications. The nanocatalyst was characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption/desorption analysis, thermograviametric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray (EDX) spectroscopy, x-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). The thermoresponsive behavior of the synthesized nanocatalyst was analyzed by UV–vis spectroscopy (UV–vis) and DLS analysis. The distribution of bimetallic nanoparticles and their compositions on the polymer-coated mesoporous silica surface were investigated by EDX mapping analysis. The specific surface area was characterized by nitrogen adsorption/desorption analysis. The nanocatalyst was tested for the catalytic reduction of benzaldehyde by UV–vis analysis. Interestingly, the bimetallic nanoparticle-supported MCM-41/p-NIPAM nanocatalyst showed higher activity compared to the other counterparts. In addition, the nanocatalyst showed thermoresponsive behavior at different temperatures and could be recycled for consecutive five cycles with minimal loss in activity. This study is expected to open promising probability for the use of the above material for a range of catalytic applications.

Insights into Compositional and Structural Effects of Bimetallic Hollow Mesoporous Nanospheres toward Ethanol Oxidation Electrocatalysis.

A one-pot soft-templating method is reported to fabricate nanosized bimetallic PdAg hollow mesoporous nanospheres (HMSs) for electrocatalytic ethanol oxidation reaction (EOR). The synthesis relies on the "dual-template" surfactant of dioctadecyldimethylammonium chloride that drives in situ growth of mesoporous frameworks on the surface of vesicles into the HMSs with radially opened mesochannels. The synthetic protocol is extendable to engineer elemental compositions and hierarchical nanostructures of PdAg nanoalloys. This system thus provides a direct yet solid platform to understand catalytic add-in synergies of PdAg HMSs toward electrochemical EOR. By evaluating compositional and structural features separately, bimetallic Pd65Ag35 HMSs display the highest EOR activity with a mass activity of 4.61 A mgPd-1. Mechanism studies indicate that synergistically electronic and bifunctional effects as well as structural advantages of Pd65Ag35 HMSs kinetically optimize the removal of poisoning carbonaceous intermediates and accelerate the diffusion processes (the rate-determining step), and thus promote the EOR performance accordingly.

Trace-level determination of amlodipine besylate by immobilization of palladium-silver bi-metallic nanoparticles on reduced graphene oxide as an electrochemical sensor

Bi-metallic PdAg was homogeneously dispersed on reduced graphene oxide (rGO) nanosheets and was synthesized by reducing ethylene glycol. Pd-Ag/rGO nanocomposite was fabricated on GCE using a drop-casting method for sensing of amlodipine and was characterized using transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). This nanocomposite exhibited excellent electrooxidative behavior of amlodipine in 0.1M PBS buffer at pH6.0. The anodic peak current of amlodipine was observed at a potential of 0.7V. Moreover, the proposed sensor exhibited superior sensitivity for the detection of AML with a linear range from 0.01 to 0.14μM with LOD=0.007μM. The effectiveness of the proposed Pd-Ag/rGO sensor was tested using the DPV technique for simultaneous detection of amlodipine, paracetamol, and dopamine in both biological and pharmaceutical samples with satisfactory results.

Transition metal nanoparticle catalysts in releasing hydrogen from the methanolysis of ammonia borane

Ammonia borane (H3N·BH3, AB) is one of the promising hydrogen storage materials due to high hydrogen storage capacity (19.6% wt), high stability in solid state as well as in solution and nontoxicity. The methanolysis of AB is an alternative way of releasing H2 due to many advantages over the hydrolysis such as having high stability against self releasing hydrogen gas. Here we review the reports on using various noble or non-noble metal(0) catalysts for H2 release from the methanolysis of AB. Ni(0), Pd(0), and Ru(0) nanoparticles (NPs), stabilized as colloidal dispersion in methanol, are highly active and long lived catalysts in the methanolysis of AB. The catalytic activity, lifetime and reusability of transition metal(0) NPs show significant improvement when supported on the surface of solid materials. The supported cobalt, nickel, copper, palladium, and ruthenium based catalysts are quite active in H2 release from the methanolysis of AB. Rh(0) NPs are highly active catalysts in releasing H2 from the methanolysis of AB when confined within the void spaces of zeolite or supported on oxide nanopowders such as nanosilica, nanohydroxyapatite, nanoalumina or nanoceria. The oxide supported Rh(0) NPs can provide high activity with turnover frequency values as high as 218 min−1 and long lifetime with total turnover values up to 26,000 in generation of H2 from the methanolysis of AB at 25 °C. When deposited on carbon the bimetallic AgPd alloy nanoparticles have the highest activity in releasing H2 through the methanolysis of AB.

Advantageous Interfacial Effects of AgPd/g-C3 N4 for Photocatalytic Hydrogen Evolution: Electronic Structure and H2 O Dissociation.

Bimetallic AgPd nanoparticles have been synthesized before, but the interfacial electronic effects of AgPd on the photocatalytic performance have been investigated less. In this work, the results of hydrogen evolution suggest that the bimetallic AgPd/g-C3 N4 sample has superior activity to Ag/g-C3 N4 and Pd/g-C3 N4 photocatalysts. The UV/Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, CO adsorption diffuse reflectance FTIR spectroscopy, and FTIR results demonstrate that in the AgPd/g-C3 N4 , the surface electronic structures of Pd and Ag are changed, which is beneficial for faster photogenerated electron transfer and greater H2 O molecule adsorption. In situ ESR spectra suggest that, under visible light irradiation, there is more H2 O dissociation to radical species on the AgPd/g-C3 N4 photocatalyst. Furthermore, DFT calculations confirm the interfacial electronic effects of AgPd/g-C3 N4 , that is, Pdδ- ⋅⋅⋅Agδ+ , and the activation energy of H2 O molecule dissociation on AgPd/g-C3 N4 is the lowest, which is the main contributor to the enhanced photocatalytic H2 evolution.

Ultrathin PdAg single-crystalline nanowires enhance ethanol oxidation electrocatalysis

Rational design and synthesis of highly efficient nanocatalysts towards electrochemical ethanol oxidation reaction (EOR) are of great importance for practical applications in direct ethanol fuel cells. Nanoengineering the nanostructures and compositions of EOR electrocatalysts has been of significnat interest because these paratmeters can enhance electrocatalytic kinetics and performance in the EOR. This article reports a synergistic EOR catalyst with remarkably enhanced electrochemical performance based on 3-nm-thick bimetallic PdAg single-crystalline nanowires. Kinetically stable yet thermodynamically unfavorable ultrathin PdAg single-crystalline nanowires (sNWs) are epitaxially grown in situ along nanoconfined hexagonal mesophases directly self-assembled by amphiphilic surfactants of dioctadecyldimethylammonium chloride under optimal synthetic condtions in aqueous solution. Due to the ultrathin and ultralong nanostructure, single-crystalline feature with a high density of low-coordinate atomic steps, high Pd utilization efficiency, and incorporation of more oxophilic Ag with Pd, PdAg sNWs show enhanced mass activity of 2.84 A mgPd−1 and stability (retained 43% after 2500 cycles) in the EOR. The kinetic studies reveal that significant enhancement in EOR performance can be ascribed to the synergic electronic and bifunctional effects of ultrathin PdAg sNWs.

Hydrodechlorination of 1,2-dichloroethane on supported AgPd catalysts

AgPd catalysts have been synthesized on SiO2, TiO2, and carbon supports using controlled surface reactions to form well defined active site structures. These catalysts were studied for hydrodechlorination of 1,2-dichloroethane to form ethane, ethylene, and chloroethane. The formation of bimetallic AgPd structures is most effective for AgPd/TiO2, followed by AgPd/C and then AgPd/SiO2 catalysts. FTIR spectra of adsorbed CO suggest that Pd is well dispersed on the Ag nanoparticles for the TiO2-supported catalyst, while more contiguous Pd sites are present on the SiO2-supported catalyst. Ethylene selectivities of up to 97% and 82% are achieved on AgPd/TiO2 and AgPd/C catalysts, respectively. The AgPd/SiO2 catalyst is 91% selective to ethane. These results indicate that the well dispersed Pd achieved at low Pd loadings on TiO2 and carbon is selective to ethylene, while the contiguous Pd species formed on SiO2 are selective to ethane. Furthermore, increased reactivity is correlated to high ethylene selectivity.

Visible light-mediated and water-assisted selective hydrodeoxygenation of lignin-derived guaiacol to cyclohexanol

Hydrodeoxygenation of lignin-derived guaiacol is achieved by magnetically separable bimetallic AgPd supported on carbon nitride using formic acid as H2 source; nitride support is obtainable via calcination of chitosan, a marine-derived renewable waste material.

Decomposition of formic acid using tungsten(VI) oxide supported AgPd nanoparticles

Formic acid (FA) is a crucial liquid H2 storage material due to its high gravimetric energy density. Therefore, dehydrogenation of FA using catalysts has attracted considerable attention. However, it is still a challenge to find a selective and active catalyst for this reaction. Bimetallic AgPd nanoparticles are well known combination to obtain efficient catalysts for the dehydrogenation of FA. Therefore, many efforts have been devoted on finding suitable supporting materials to increase the efficiency of AgPd NPs in dehydrogenation of FA. In this study, tungsten(VI) oxide, WO3 was used as a supporting material due to its multiple oxidation states which play an important role for obtaining highly efficient catalyst. Herein, bimetallic AgPd nanoparticles supported on WO3 were successfully prepared. The activity of AgPd/WO3 catalysts with different Ag loading was tested in dehydrogenation of FA in presence of sodium formate at 50.0 ± 0.1 °C. Ag0.25Pd/WO3 catalyst with a TOF value of 683 h−1 exhibited high activity in this reaction. In addition, the effect of sodium formate on the decomposition of formic acid was investigated in detail.

Model Bimetallic Pd–Ag/HOPG Catalysts: An XPS and STM Study

A series of model bimetallic Pd–Ag catalysts with different ratios of metals and size distributions of supported particles was prepared by successive metal deposition onto a modified surface of highly oriented pyrolytic graphite (HOPG). X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the structural and electronic properties, as well as the morphology of nanoparticles at all stages of catalyst preparation. The use of the method made it possible to obtain bimetallic particles with various structures: alloyed, core–shell, and those consisting of individual monometallic particles. The XPS method with synchrotron radiation was used to determine the patterns in the formation of alloyed bimetallic particles, their chemical composition, structure, and the ranges of thermal stability under conditions of ultrahigh vacuum.