PdCu Nanoalloy Research Articles

Effect of addition of iron on morphology and catalytic activity of PdCu nanoalloy thin film as catalyst in Sonogashira coupling reaction

Palladium‐supported catalysts are complex assemblies with a challenging preparation. Minor changes in their preparation conditions can affect the activity, selectivity and lifetime of these catalysts. PdCuFe nanoparticle (NP) thin films were supported on reduced graphene oxide (RGO) by the reduction of the organometallic complex [PdCl2‌(cod)] (cod = cis,cis‐1,5‐cyclooctadiene), and [Cu(acac)2] and [Fe(acac)3] (acac = acetylacetonate) complexes at a toluene–water interface. We have investigated the application of the liquid–liquid interface method for preparing ultrathin films of catalysts and have evaluated the catalytic activity of the prepared NPs for the Sonogashira coupling reaction in micelle media. Also, we have investigated the effect of the addition of iron on the morphology, size and catalytic activity of PdCu/RGO NPs. Our study shows that both of the prepared catalysts (PdCu/RGO and PdCuFe/RGO) are efficient and recoverable catalysts for the Sonogashira carbon–carbon coupling reaction. This method has advantages compared to other routes, such as short reaction times, high to excellent yields, facile and low‐cost method for the preparation of the catalysts, and easy separation and reusability of the catalysts.

High‐Performance Electrocatalytic Activity of Palladium‐Copper Nanoalloy towards Methanol Electro‐oxidation in an Alkaline Medium

AbstractNanoalloy of PdCu were synthesized with three different stoichiometry ratio (3 : 1, 1 : 1, 1 : 3) by simple co‐reduction process at 5 °C with Triton X‐100 as surface modifier. Morphology and composition of the synthesized catalyst were characterized by X‐ray diffraction (XRD), X‐ray photo electron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X‐ray analysis (EDAX) with selected area electron diffraction (SAED) techniques. Electrocatalytic activity and stability of the catalysts towards methanol oxidation reaction were verified in alkaline medium by cyclic voltammetry (CV) and chronoamperometry (CA). Observed results emphasis that PdCu nanoalloy in the 3 : 1 stoichiometric ratio shows better catalytic activity (778.98 mA mg−1) and stability not only in the initial state (93.73 mA mg−1) but also after 1800 s (8.61 mA mg−1) among all other prepared catalysts.

Synergistic catalytic properties of bifunctional nanoalloy catalysts in rechargeable lithium-oxygen battery

Abstract The understanding of factors influencing the performance of catalysts in the air cathode of a rechargeable lithium-oxygen battery, including overpotentials for oxygen reduction/evolution and discharge capacity, is essential for exploration of its ultimate application. This report describes new findings of an investigation of PdCu nanoalloys as cathode catalysts. Alloying Pd with oxophilic base metals such as Cu leads to reduction of the overpotentials and increase of the discharge capacity. The nanoalloy structures depend on the bimetallic composition, with an atomic ratio near 50:50 featuring mixed bcc and fcc structures. The discharge potential exhibits a maximum while the charge potential display a minimum in the range of 20–50% Cu, closer to 25% Cu, both of which correspond to a maximum reduction of the discharge-charge overpotentials. The discharge capacity displays a gradual increase with Cu%. This type of catalytic synergy is believed to be associated with a combination of ensemble and ligand effects. In particular, the activation of oxygen on Pd sites and oxygen oxophilicity at the alloyed Cu sites in the catalyst may have played an important role in effectively activating oxygen and maneuvering surface superoxide/peroxide species. These findings have implications for the design of multifunctional cathode catalysts in rechargeable lithium-oxygen batteries.

Catalytic performance of Pd-promoted Cu hydrotalcite-derived catalysts in partial hydrogenation of acetylene: effect of Pd–Cu alloy formation

A highly dispersed PdCu nanoalloy catalyst derived from a CuMgAl-hydrotalcite precursor exhibited superior catalytic performance in partial hydrogenation of acetylene.

PdCu Nanoalloy Electrocatalysts in Oxygen Reduction Reaction: Role of Composition and Phase State in Catalytic Synergy.

The catalytic synergy of nanoalloy catalysts depends on the nanoscale size, composition, phase state, and surface properties. This report describes findings of an investigation of their roles in the enhancement of electrocatalytic activity of PdCu alloy nanoparticle catalysts for oxygen reduction reaction (ORR). Pd(n)Cu(100-n) nanoalloys with controlled composition and subtle differences in size and phase state were synthesized by two different wet chemical methods. Detailed electrochemical characterization was performed to determine the surface properties and the catalytic activities. The atomic-scale structures of these catalysts were also characterized by high-energy synchrotron X-ray diffraction coupled with atomic pair distribution function analysis. The electrocatalytic activity and stability were shown to depend on the size, composition, and phase structure. With Pd(n)Cu(100-n) catalysts from both methods, a maximum ORR activity was revealed at Pd/Cu ratio close to 50:50. Structurally, Pd50Cu50 nanoalloys feature a mixed phase consisting of chemically ordered (body-centered cubic type) and disordered (face-centered cubic type) domains. The phase-segregated structure is shown to change to a single phase upon electrochemical potential cycling in ORR condition. While the surface Cu dissolution occurred in PdCu catalysts from the two different synthesis methods, the PdCu with a single-phase character is found to exhibit a tendency of a much greater dissolution than that with the phase segregation. Analysis of the results, along theoretical modeling based on density functional theory calculation, has provided new insights for the correlation between the electrocatalytic activity and the catalyst structures.

Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale.

The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo phase segregation into distinct chemically-ordered (B2-type) and disordered (fcc-type) domains. This finding is significant since it provides a rational basis for streamlining the design and preparation of Pd-based nanoalloy catalysts in terms of atomic structure and phase state.