PdCu Nanoparticles Research Articles

Novel bimetallic nanoporous Pd-Cu-SBA-16/CPE as a highly sensitive sensor for determination of formaldehyde

The incorporation of catalysts in mesoporous materials with high surface area is an interesting approach to improve the efficiency of them. Also, the formation of bimetallic nanocatalyst is a new way to decrease the amount of precious noble metal catalyst. In this work, the nanoporous SBA-16 is successfully synthesized from stem sweep as a silica source and characterized by X-ray diffraction, scanning electron microscopy, transition electron microscopy, Furrier transform infrared spectroscopy and Brunauer-Emmett–Teller techniques. The synthesized SBA-16 is applied as a nanoporous support to fabricate novel SBA-16-supported bimetallic Pd-Cu nanoparticle electrochemical sensor for determination of formaldehyde. This sensor is simply prepared using galvanic replacement method and without using any linking agent. The elemental composition of as-prepared electrochemical sensor is investigated by energy dispersive spectrometry. Also, the electrochemical performance of prepared sensor toward formaldehyde oxidation is studied by cyclic voltammetry, amperometry and chronoamperometry methods. The cyclic voltammetry results show improved electrocatalytic activity including high current density and low overpotential for oxidation of formaldehyde. Moreover, the amperometric measurements show that this sensor can detect formaldehyde in the linear range of 1.79mM to 121.86mM with detection limit of 16μM at a signal-to-noise ratio of 3 and response time of 3s. Furthermore, this sensor shows good stability, repeatability, reproducibility and selectivity.

Highly Active and Selective Hydrogenation of CO2 to Ethanol by Ordered Pd-Cu Nanoparticles.

Carbon dioxide (CO2) hydrogenation to ethanol (C2H5OH) is considered a promising way for CO2 conversion and utilization, whereas desirable conversion efficiency remains a challenge. Herein, highly active, selective and stable CO2 hydrogenation to C2H5OH was enabled by highly ordered Pd-Cu nanoparticles (NPs). By tuning the composition of the Pd-Cu NPs and catalyst supports, the efficiency of CO2 hydrogenation to C2H5OH was well optimized with Pd2Cu NPs/P25 exhibiting high selectivity to C2H5OH of up to 92.0% and the highest turnover frequency of 359.0 h-1. Diffuse reflectance infrared Fourier transform spectroscopy results revealed the high C2H5OH production and selectivity of Pd2Cu NPs/P25 can be ascribed to boosting *CO (adsorption CO) hydrogenation to *HCO, the rate-determining step for the CO2 hydrogenation to C2H5OH.

Pd and Cu-Pd nanoparticles supported on multiwall carbon nanotubes for H2 detection

Simple, cost-effective, and reproducible devices have been prepared for the detection of H2 at room temperature. Pd, Cu and bimetallic Cu-Pd nanoparticles (prepared by the reduction-by-solvent method) have been loaded on a MWCNT deposit avoiding the use of surfactants or complicated techniques. The devices based on pure Pd nanoparticles have shown a high H2 sensitivity in the studied H2 concentration range with low response and recovery times. However, the addition of Cu in the metallic nanoparticles does not result in a considerable improvement. Furthermore, the Pd and Cu-Pd/MWCNTs-based sensors have kept part of their H2 sensitivity when they have been tested in an O2-depleted atmospheres, which is an altogether new finding compared to Pd-based systems. Through these experiments it has been possible to conclude how the main H2 detection mechanism is the electron transfer from the nanoparticles (when the PdHx is formed) to the carbon nanotubes.

Cold Plasma for Synthesizing High Performance Bimetallic PdCu catalysts: Effect of Reduction Sequence and Pd/Cu Atomic Ratios

Alumina supported bimetallic PdCu catalysts were prepared by simple incipient wetness impregnation followed by the process of atmospheric-pressure cold plasma reduction using Pd(NO3)2 and Cu(NO3)2 as Pd and Cu precursors, respectively. The influence of reduction sequence and Pd/Cu atomic ratios on the structure and performance of the catalysts were investigated. The highest CO oxidation activity was obtained for the PdCu catalyst (PdCu/Al2O3–P) prepared by co-impregnation and reduction of the Pd and Cu precursors with a Pd/Cu atomic ratio of 1:1. Meantime, the PdCu/Al2O3–P catalyst prepared by cold plasma exhibits much higher performance than that prepared by conventional thermal reduction. The optimum results from the alloying degree, crystallite size and dispersion of PdCu nanoparticles, and the chemisorbed oxygen species on the surface of the support. As a result of the interaction between Pd and Cu species, high alloying degree, small size and high dispersion of PdCu nanoparticles in PdCu/Al2O3–P were obtained. In addition, due to the fast (6 min reduction) and low temperature reduction process, more active chemisorbed oxygen species were formed on the surface of PdCu/Al2O3–P. The results of diffuse reflectance fourier transform infrared and catalytic stability show that the interaction between Pd and carbon species is weakened, which may facilitate the adsorption and activation of O2. These make PdCu/Al2O3–P an excellent catalyst for CO oxidation. Atmospheric-pressure cold plasma is proved to be a facile and efficient method for fabricating high performance bimetallic PdCu catalysts, which may have potential applications for preparing other bimetallic catalysts.

PdCu Nanoparticles Stabilized on Porous CeO2 for Catalytic Degradation of Azo Dyes: Structural Characterization and Kinetic Studies

AbstractIn this work, a series of porous CeO2 stabilized PdCu nanoparticles are synthesized by a modified hydrothermal method and applied for catalytic reductive degradation of azo dyes. For the synthesis of CeO2 support a simple precipitation method is adopted using ammonium oxalate as precipitant. Synthesized support and nanoparticles are characterized by XRD, TGA, BET surface area, SEM/EDX, TEM, Raman, UV‐visible DRS, FTIR and XPS analyses. Catalytic studies show that the synthesized nanoparticles can efficiently reduce model azo dyes, methyl orange (MO) and congo red (CR) with good recyclability. Among various PdCu compositions, Pd1Cu9/CeO2 exhibits superior catalytic activity towards reductive degradation of MO and CR at room temperature. Thus, PdCu/CeO2 nanoparticles can be accepted as potential component for the application in wastewater treatment.

Synthetically Tuned Atomic Ordering in PdCu Nanoparticles with Enhanced Catalytic Activity toward Solvent-Free Benzylamine Oxidation.

Synthesis of ordered compounds with nano size is of particular interest for tuning the surface properties with enhanced activity and selectivity toward various important industrial catalytic processes. In this work, we synthesized ordered PdCu nanoparticles as highly efficient catalyst for the solvent-free aerobic oxidation of benzylamine. The PdxCu1-x catalysts with different chemical compositions (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) were prepared by polyol method using NaBH4 as a reducing agent and were well-characterized by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) energy-dispersive analysis of X-rays, and X-ray absorption fine structure. The effect of different metal concentrations of Pd and Cu on the formation of PdxCu1-x nanoparticles was investigated. The XRD and TEM confirmed the formation of ordered PdCu intermetallic phase with body-centered cubic (BCC) structure for the synthetic composition of Pd/Cu = 1:1. For compositions x = 0, 0.25, 0.75, and 1, PdxCu1-x alloy with face-centered cubic (FCC) structure was observed, whereas mixed phase of BCC and FCC was observed for x = 0.4 and 0.6. The use of strong reducing agent (NaBH4) was essential to synthesize PdCu ordered phase compared to weak reducing agents such as oleylamine and ascorbic acid. The PdCu nanocatalyst with ordered structure (BCC) showed excellent catalytic activity compared to PdxCu1-x alloy nanoparticles with FCC structure. The atomic ordering in the PdCu intermetallic was the driving force for the enhancement in the catalytic activity with high benzylamine conversion of 94.0% and dibenzylimine selectivity of 92.2% compared to its monometallic and alloy counterparts. Moreover, ordered PdCu alloy showed good recyclability and activity toward the oxidation of different amines.

Bimetallic Cu-Pd Nanoparticles Supported on Bio-silica as an Efficient Catalyst for Selective Aerobic Oxidation of Benzylic Alcohols

A new bimetallic heterogeneous catalyst consisting of copper and palladium nanoparticles supported on bio-silica is presented. The use of TEMPO as co-catalyst allowed the aerobic oxidation of primary benzylic alcohols into the corresponding aldehydes with excellent selectivity and good activity. The methodology could be applied to the oxidation of allylic and heterobenzylic alcohols. The catalyst is easy to prepare from commercial starting materials and can be recovered and reused without apparent loss of activity.

In-situ X-ray absorption study of ceria-supported Pd-Cu nanoparticles for oxygen-enhanced water gas shift

The detailed structures of bimetallic Pd-Cu on various CeO2 and Al2O3 supports were investigated by X-ray absorption technique in-situ in hydrogen and WGS conditions. No indication of the neighboring Pd atoms in both Pd-K edge and Cu-K edge EXAFS fittings showed that Pd is highly dispersed in the lattice of metallic Cu. The Cu-Cu bond distance was markedly shortened by alloying with Pd and correlated to decrease of coordination number, which reflects particle size. A higher coordination number for Pd-Cu than that for Cu-Cu on Al2O3 support suggested that Pd is in the interior of the nanoparticles on Al2O3 while these coordination numbers were close on CeO2 support indicating a uniform distribution of Pd and Cu atoms. The CO shift activity was not simply correlated to the Cu-Cu bond distance or particle size, but the high activity of Pd-Cu/CeO2 was attributed to surface Pd interacting with Cu on CeO2 surface.

Synergistic Catalysis with MIL-101: Stabilized Highly Active Bimetallic NiPd and CuPd Alloy Nanoparticle Catalysts for C-C Coupling Reactions

Highly active bimetallic NiPd/MIL-101, CuPd/MIL-101 and CoPd/MIL-101 alloy nanoparticle catalysts stabilized by MIL-101 framework, (M/Pd atomic ratio=95:5, M=Ni, Cu and Co) were synthesized, and their catalytic activity for Suzuki reaction at moderate reaction conditions was explored. In contrary to monometallic counterparts, a significant enhancement in catalytic activity, with excellent yields for biaryls (upto 97 %), was observed with these bimetallic NiPd/MIL-101, CuPd/MIL-101 and CoPd/MIL-101 alloy nanoparticle catalysts. Among these catalysts, NiPd/MIL-101 and CuPd/MIL-101 displayed highest catalytic activity for the synthesis of biaryls for a wide range of substituted aryl halides and arylboronic acids with electron donating and electron withdrawing substituents, whereas CoPd/MIL-101 was found to be poorly active. Worthy to mention that, NiPd/MIL-101 and CuPd/MIL-101 displayed ca 20 times higher TOF (h−1) than the Pd/MIL-101 catalyst. The observed high catalytic activity displayed by NiPd/MIL-101 and CuPd/MIL-101 was attributed to the synergistic effect due to electronic charge transfer from Ni or Cu to Pd, and high dispersion of NiPd and CuPd nanoparticles on MIL-101 frameworks.

Size-Dependent Disorder-Order Transformation in the Synthesis of Monodisperse Intermetallic PdCu Nanocatalysts.

The high performance of Pd-based intermetallic nanocatalysts has the potential to replace Pt-containing catalysts for fuel-cell reactions. Conventionally, intermetallic particles are obtained through the annealing of nanoparticles of a random alloy distribution. However, this method inevitably leads to sintering of the nanoparticles and generates polydisperse samples. Here, monodisperse PdCu nanoparticles with the ordered B2 phase were synthesized by seed-mediated co-reduction using PdCu nanoparticle seeds with a random alloy distribution (A1 phase). A time-evolution study suggests that the particles must overcome a size-dependent activation barrier for the ordering process to occur. Characterization of the as-prepared PdCu B2 nanoparticles by electron microscopy techniques revealed surface segregation of Pd as a thin shell over the PdCu core. The ordered nanoparticles exhibit superior activity and durability for the oxygen reduction reaction in comparison with PdCu A1 nanoparticles. This seed-mediated co-reduction strategy produced monodisperse nanoparticles ideally suited for structure-activity studies. Moreover, the study of their growth mechanism provides insights into the size dependence of disorder-order transformations of bimetallic alloys at the nanoscale, which should enable the design of synthetic strategies toward other intermetallic systems.

Synthesis of carbon supported Au-decorated PdCu nanocatalyst for formic acid oxidation

This work reports the synthesis of a novel carbon supported Au-decorated PdCu composite catalyst for formic acid oxidation. The catalyst was prepared through a two-step process. PdCu alloy was firstly prepared through co-reduction of Pd and Cu ions using ethylene glycol and sodium citrate as the reducing and stabilizing reagents. Au was decorated on the surface of the PdCu alloy through spontaneous replacements of Pd and Cu by Au. Transmission electron microscopy (TEM) image shows that the metallic nanoparticles are well dispersed on the carbon surface. X-ray photoelectron spectroscopy (XPS) results demonstrate that the Pd 3d5/2 binding energy (BE) of the PdCu@Au/C exhibits a positive shift in comparison with that of Pd/C and PdCu/C. The as-prepared composite catalyst exhibits higher activity towards formic acid oxidation in comparison with individual Pd. Interestingly, a significantly improved electrochemical stability of Au-decorated PdCu nanoparticles compared with the PdCu counterpart is observed.

CuPd nanoparticles as a catalyst in carbon–carbon cross-coupling reactions by a facile oleylamine synthesis

CuPd bi-metallic nanoparticles prepared by facile oleylamine synthesis as an efficient catalyst in carbon–carbon cross-coupling reactions with multiple recyclability and excellent turnover frequency.

Carbon Supported CuPd Nanoparticles for Sensitive Detection and Electrocatalytic Reduction of m-Nitrophenol

Nitrophenols are important chemicals widely used and caused toxic effects on living beings. Here we developed a facile method to prepare CuPd/C catalyst for both m-nitrophenol sensitive detection (1 μM) and electrocatalytic reduction in a wide range from 100 to 10000 μM. The CuPd nanoparticles was synthesized by controlled coreduction of Cu and Pd salts in oleylamine and dispersed on carbon black to produce CuPd/C catalysts. The CuPd/C catalyst was subsequently modified on glassy carbon electrode both as the detection sensor and to investigate electrocatalytic reduction of m-nitrophenol. The sensitivity on the CuPd/C modified electrode (CuPd/C/GCE) was much higher than that on the GCE or commercial Pd/C modified electrode (Pd/C/GCE). The CuPd/C nanomaterial shows excellent m-nitrophenol sensing capability, including low detection limit, wide linear range, high reproducibility and stability. That makes it a unique electrochemical sensor for the detection of m-nitrophenol. The influence of m-nitrophenol concentration on the electrocatalytic ability of the CuPd/C/GCE was studied, and the reduction mechanism of m-nitrophenol is also presented.

Hollow PdCu nanocubes supported by N-doped graphene: A surface science and electrochemical study

N doped graphenes (NGs) are believed to be promising materials for constructing novel hybrid composites with desirable functionalities and applications in many fields. Therefore, a better understanding of the NGs holds the key to a better performance of the hybrid properties. A facile and low-cost preparation of NGs supported hollow PdCu alloy nanocubes (H–PdCu) catalysts were introduced in this paper. To increase the stability and efficiency of the catalysts, a two-step strategy was employed, which included the preparation of NGs and the synthesis of hollow PdCu alloy nanocube catalysts. A series of NGs using melamine, polypyrrole (ppy) and polyaniline (PANI) as nitrogen source, respectively. The influence of the different N species (pyridinic N, pyrrolic N and graphite N) on the morphologies and corresponding electrical properties of H–PdCu nanoparticles were studied. The results indicate that NGs are successfully synthesized, and hollow PdCu alloy nanocubes are well-dispersed on the surface of them with a relatively narrow particle size distribution. Electrochemical characterizations reveal that the H–PdCu/melamine-NG catalyst has excellent catalytic activity and stability toward alcohols oxidation in alkaline electrolyte, which can serve as promising anode catalysts in direct alcohols fuel cells (DAFCs).

Electrocatalytic Properties of Carbon Nanotubes Decorated with Copper and Bimetallic CuPd Nanoparticles

Copper particles were deposited on the surface of palladium decorated buckypapers by the means of chemical plating, in which the palladium nanoparticles act as catalyst for initiating the reduction of complexed Cu2+ ions in the presence of formaldehyde. By adjusting the plating time, it is possible to tune the size of the highly crystalline copper particles and at the same time control the coverage of the metal on the surface of carbon nanotubes. In a subsequent step, the copper particles were partially exchanged with palladium to obtain bimetallic CuPd nanoparticles on the nanotubes by applying galvanic replacement reactions in aqueous solution of Pd2+ ions. Sufficiently high electrical conductivity of both Cu and CuPd/buckypaper composites makes them suitable to be used as electrocatalytic electrodes. The electrochemical properties of the different electrode materials were also evaluated by the model reaction of methanol electrooxidation. The degradation mechanism of copper and CuPd bimetallic catalysts were systematically studied by employing surface characterization techniques on the composite films after electrocatalytic testing in alkaline solution in the presence and absence of methanol. Chronoamperometric test of the catalysts/buckypaper composites had revealed that palladium plays a protecting role in CuPd bimetallic structure during methanol electrooxidation.

Monodisperse MPd (M: Co, Ni, Cu) alloy nanoparticles supported on reduced graphene oxide as cathode catalysts for the lithium-air battery

Addressed herein is the electrocatalyst performance of the monodisperse MPd (M: Co, Ni, Cu) alloy nanoparticles (NPs) supported on reduced graphene oxide (rGO) for the non-aqueous Li-air battery. MPd alloy NPs were prepared by using a well-established surfactant-assisted organic solution phase protocol comprising the co-reduction of palladium(II) acetylacetonate and M(acetate)2 or M(acetylacetonate)2 by borane-based mild reducing agents in oleylamine. As-synthesized Co3Pd7, Ni3Pd7 and CuPd NPs have uniform particle size distribution with the average particle size of 3.5, 3.4 and 3.0 nm, respectively. The colloidal MPd NPs were then supported on rGO before their use as cathode catalysts in the non-aqueous Li-air battery. The charge–discharge curves of Li-air electrodes using rGO-CuPd, rGO-Co3Pd7 and rGO-Ni3Pd7 catalysts were investigated at a current rate of 100 mA g−1. The specific discharge capacities were found as 4407 mA h g−1 for rGO-CuPd, 3158 mA h g−1 for rGO-Co3Pd7 and 2512 mA h g−1 for rGO-Ni3Pd7. Ex-situ FTIR analyses after the 10 cycle recyclability test revealed that Li2O2 is the main component of the discharge products. The lifetime of the cathode electrodes during the first 10 cycles was found to be 100 h for rGO-Co3Pd7, 130 h for rGO-CuPd and 180 h for rGO-Ni3Pd7. The Ni3Pd7 has the highest total capacity of 8175 mA h g−1 over the first 10 cycles.

Carbon supported Cu-Pd nanoparticles as anode catalyst for direct borohydride-hydrogen peroxide fuel cells

Carbon supported Cu-Pd bimetallic nanoparticles were prepared by a successive reduction method in aqueous solution and used as anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronopotentiometry (CP), linear sweep voltammetry (LSV) and fuel cell test. The results show that the size of the crystallite is around 12.5nm, the Cu1Pd1/C catalyst presents the highest catalytic activity among all the resultant catalysts, and the DBHFC using Cu1Pd1/C as anode catalyst and Pt mesh (1cm×1cm) as cathode electrode obtains the maximum power density as high as 39.8 mW cm-2 at a discharge current density of 80.1mA cm-2 at 20°C.

ChemInform Abstract: Preparation of Carbon Supported CuPd Nanoparticles as Novel Heterogeneous Catalysts for the Reduction of Nitroarenes and the Phosphine‐Free Suzuki—Miyaura Coupling Reaction.

AbstractCarbon‐supported bimetallic CuPd nanoparticles are shown to be an efficient catalyst for the reduction of nitrorarenes and for the phosphine‐free Suzuki—Miyaura coupling reaction.

Preparation of carbon supported CuPd nanoparticles as novel heterogeneous catalysts for the reduction of nitroarenes and the phosphine-free Suzuki–Miyaura coupling reaction

This paper reports on the synthesis and use of C/CuPd bimetallic NPs as heterogeneous catalysts for the phosphine-free Suzuki–Miyaura coupling and the reduction of nitroarenes.

Bimetallic PdCu Nanoparticle Catalyst Supported on Hydrotalcite for Selective Aerobic Oxidation of Benzyl Alcohol

ABSTRACTTo decrease the amount of precious metal usage for Pd-catalyzed aerobic alcohol oxidation, various amount of Cu-contained Pd bimetallic nanoparticle-supported solid base hydrotalcite catalyst (PdxCuy-PVP/HTs) were prepared and applied for aerobic benzyl alcohol oxidation. It was found that the addition of Cu atoms into Pd in the range of 0-40% provided a similar or a little superior activity to that of Pd100-PVP catalyst, whereas a large quantity of co-existence Cu (>40%) gradually decreased their activity of the catalyst. The aerobic benzyl alcohol oxidation over Pd80Cu20-PVP/HT served 77% yield and 95% selectivity towards benzaldehyde at 313 K for 5 h in toluene under O2 flow. X-ray adsorption spectroscopy (XAS) studies and scanning transmission electron microscopy-high angle annuar dark field (STEM-HAADF) with energy dispersive X-ray spectroscopy (EDS) analyses suggested that Cu atoms doping into Pd(0) NP influenced not only localized nanostructure but also oxidation state around Pd atoms. We suggested that substitution of precious metal with small amount of transition metals such as Cu lead to geometric/electronic changes in active sites would be one of nice strategies for reducing the cost for the catalyst in the oxidation process.