Palladium Cobalt Alloy Research Articles

Study of the Influence of Ferromagnetic Impurity Concentration on Magnetic Properties of Binary Palladium–Cobalt Alloy

A comparative study of the magnetic properties of a palladium–cobalt alloy with an impurity content of up to 0.05 at. % was made using calculations based on the density functional theory and experimental methods. It was found that the alloys had ferromagnetic ordering, which depended on the impurity concentration. At very low concentrations, less than 1 at. %, the magnetic moment per impurity atom can reach 25 µB.

Study of the Influence of Ferromagnetic Impurity Concentration on Magnetic Properties of Binary Palladium–Cobalt Alloy

Study of the Influence of Ferromagnetic Impurity Concentration on Magnetic Properties of Binary Palladium–Cobalt Alloy

Electrochemically Reduced Graphene Oxide Supported Palladium-Cobalt Alloy Nanoparticles as Highly Efficient Electrocatalyst for Oxygen Reduction Reaction

Pd-Co alloy nanoparticles were synthesized on electrochemically reduced graphene oxide (ErGO) for electrocatalytic oxygen reduction reaction (ORR) in alkaline media. The morphological structure, chemical composition, and crystallinity of the afforded ErGO/Pd-Co catalyst were examined by various techniques, including transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The Pd-Co alloy nanoparticles were evenly distributed on the ErGO sheet and had a narrow size distribution, with an average particle size of 4.25 nm. The ORR activity of the as-prepared ErGO/Pd-Co alloy catalyst was evaluated by cyclic voltammetry, linear sweep voltammetry, rotating disk electrode, and rotating ring disk electrode techniques in an alkaline electrolyte. The ErGO/Pd-Co catalyst exhibits a very high electrocatalytic activity in ORR with the mass activity more than 2.0 times of the commercial 20% Pt/C due to the synergistic catalytic effect of both ErGO and Pd-Co nanoparticles. Electrocatalytic kinetics investigation shows that, the ORR on the ErGO/Pd-Co catalyst proceeds through four electrons transferred mechanism with negligible amount of peroxide species. Moreover, the ErGO/Pd-Co shows an excellent methanol tolerance than the commercial 20% Pt/C.

Correlation among hydrogenation, magnetoelastic coupling, magnetic anisotropy, and magnetoresistance in magnetostrictive, hydrogen-absorbing palladium-cobalt alloy films for hydrogen sensing

Hydrogen-absorbing magnetic alloy films, such as palladium-cobalt (PdCo) alloy films, are expected to play a significant role in the next generation of hydrogen sensors. However, effects of hydrogenation on such films are very complex, since these alloys show strong spin-orbit interaction, i.e., strong magnetoelastic coupling. Accordingly, we conducted integrated research on the hydrogenation, magnetoelastic coupling, magnetism, and galvanomagnetic effect of PdCo alloy films having different magnetic anisotropies of longitudinal and perpendicular magnetic anisotropies. As a result, it was revealed that the stress in the film determines its magnetic anisotropy. The magnetoresistance curves of films, consisting of ordinal and anisotropic magnetoresistance effects, correspond well to the magnetization-magnetic field curves. Hydrogenation results in the compressive stress and decreased magnetostriction, which both have a negative influence on the perpendicular magnetic anisotropy energy of the films. Moreover, the influence is observed also in ordinal and anisotropic magnetoresistances. In addition, the increases in coercivity and electronic resistivity due to the incorporated hydrogen atoms (and related defects) are detected. The results are summarized in a correlation diagram, which shows that hydrogen-absorbing magnetic alloy films are very suitable for use in hydrogen sensors—the films can detect hydrogen via various methods such as magnetic anisotropy, galvanomagnetic effect, coercivity, and resistivity.

Palladium cobalt alloy encapsulated in carbon nanofibers as bifunctional electrocatalyst for high-efficiency overall hydrazine splitting

Electrolytic water splitting is a promising strategy to generate clean hydrogen energy but still restricted by the sluggish kinetics during the anodic oxygen evolution reaction (OER). A highly efficient route to significantlyreduce the cell voltage of electrolytic water splitting is to replace OER with hydrazine oxidation reaction (HzOR) so as to assist hydrogen generation effectively. Here, we report the fabrication of carbon nanofibers (CNFs) embedded with palladium cobalt (PdCo) alloy nanoparticles, via an electrospinning followed by a carbonization treatment. The as-synthesized PdCo-CNFs catalyst displays a superior electrocatalytic activity toward HzOR with a working potential of 258 mV (vs. RHE) to drive a current density of 50 mA cm−2 in an alkaline solution with 0.2 M hydrazine. Furthermore, the favorable hydrogen evolution reaction (HER) activity of this catalyst enables it highly efficient electrolytic hydrogen production, and the two-electrode system using PdCo-CNFs as both the cathode and anode for overall hydrazine splitting is capable of delivering a cell voltage of 0.440 V to attain 10 mA cm−2, which is 1.496 V less than that for pure water splitting using the same electrodes and even 0.459 V less than the overall hydrazine splitting device using Pt/C//RuO2 as electrocatalysts. This work provides a reliable way for the fabrication of promising bifunctional electrocatalysts to promote energy-saving hydrogen production for practical applications.

Origin of large magnetostriction in palladium cobalt and palladium nickel alloys: Strong pseudo-dipole interactions between palladium–cobalt and palladium–nickel atomic pairs

The origin of the large magnetostriction in palladium cobalt and palladium nickel alloys was investigated. Density functional theory calculations based on the Korringa–Kohn–Rostoker Green function method with the coherent potential approximation revealed that alloying with palladium results in increased magnetization of cobalt and nickel atoms. Also, anomalous magnetization of palladium atoms occurs simultaneously. Employing calculated spin and orbital angular momenta of the atoms, magnetostriction was discussed based on the two-spin model for disordered alloys. Under the assumption that the pseudo-dipole interaction is proportional to the orbital and total angular momenta, the experimental magnetostriction curves can be reproduced. The estimated contributions of each atomic pair to magnetostriction revealed that the large magnetostriction at the palladium-rich side originates from the strong pseudo-dipole interactions between 4d and 3d transition metal atoms, namely, palladium–cobalt and palladium–nickel atomic pairs.

Retraction: Monodispersed palladium-cobalt alloy nanoparticles assembled on poly(N-vinyl-pyrrolidone) (PVP) as a highly effective catalyst for dimethylamine borane (DMAB) dehydrocoupling.

Retraction of ‘Monodispersed palladium–cobalt alloy nanoparticles assembled on poly(N-vinyl-pyrrolidone) (PVP) as a highly effective catalyst for dimethylamine borane (DMAB) dehydrocoupling’ by Betül Çelik et al., RSC Adv., 2016, 6, 24097–24102, DOI: 10.1039/c6ra00536e.

Effects of stress and defects on hydrogenation and magnetic properties in (111) fiber-textured palladium cobalt alloy films

Effects of stress and defects on the hydrogenation and magnetic properties of (111) fiber-textured palladium cobalt Pd92Co8 (at.%) alloy films are investigated using post-annealing process. It is revealed that the hydrogen stabilization due to tensile stress induces various effects on hydrogenation. Defect removal results in an increased solubility limit for the metallic α-phase and an increased critical hydrogen pressure to form the hydride β-phase. It was demonstrated that the local strain can depict these effects using a linear function. The improved resistance against film buckling is also attributed to the defect removal. Thus, post-annealing is a powerful process to control hydrogenation; however, the effects are complicated because various effects work in conjunction. In contrast, the magnetic properties can be explained in simple terms. The saturation magnetization corresponds linearly to the defect concentration with a negative slope, and the magnetic anisotropy is proportional to the stress due to magnetoelastic coupling.

Freestanding Single-Atom-Layer Pd-Based Catalysts: Oriented Splitting of Energy Bands for Unique Stability and Activity

Summary Freestanding and self-stabilized single-atom-layer (SAL) palladium (Pd) and palladium-cobalt (PdCo) alloy films were generated in the angstrom-sized interlayer space of layered minerals, where the metal only grows and spreads out in two dimensions. The SAL films display strongly coordinated metallic bonds in two dimensions and dangling bonds in the z direction. Under such absolute two-dimensional coordination, their valence-empty band exhibits an unusual split into a lower-energy band in the x-y plane, which promotes in-plane stability, and a higher-energy band in the z direction, which contributes to reactivity along this axis. This gives rise to exceptional properties and functions that cannot be achieved by analogs of other dimensionalities. Specifically, the SAL PdCo alloy exhibits six times higher mass activity than commercial platinum (Pt) nanoparticles in oxygen reduction. Its mass activity is also eight times higher than that of Pd nanoparticles for formic acid oxidation.

Controllable magnetic anisotropy and magnetostriction constant in palladium cobalt alloy films: Effects of composition, thickness, and stress

The magnetic anisotropy of sputter-deposited films of palladium cobalt Pd100 − xCox (x = 7, 15, and 28 at. %) alloy is investigated systematically. The exact anisotropy energies of all contributions, namely, surface, magnetocrystalline, magnetoelastic, and shape, are estimated. Using these energies, the main origin of the magnetic anisotropy is determined and summarized in maps of film thickness and film stress. Consequently, how composition, thickness, and stress affect the magnetic anisotropy is clarified. Accordingly, the controllability between longitudinal and perpendicular magnetic anisotropy is revealed. In addition, the magnetostriction constant λ111 is estimated from the change in the volume anisotropy energy due to the stress in the film, namely, the inverse magnetostrictive effect. The constant is a large negative number, −178 ppm at maximum, and agrees partially with a reference value measured under normal magnetostriction. The disagreement by 30% of the magnetostriction constant with respect to the expected value for Pd72Co28 films was elucidated by the magnetostriction enlargement by tensile stress.

High-performance Platinum-free oxygen reduction reaction and hydrogen oxidation reaction catalyst in polymer electrolyte membrane fuel cell

The integration of polymer electrolyte membrane fuel cell (PEMFC) stack into vehicles necessitates the replacement of high-priced platinum (Pt)-based electrocatalyst, which contributes to about 45% of the cost of the stack. The implementation of high-performance and durable Pt metal-free catalyst for both oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) could significantly enable large-scale commercialization of fuel cell–powered vehicles. Towards this goal, a simple, scalable, single-step synthesis method was adopted to develop palladium-cobalt alloy supported on nitrogen-doped reduced graphene oxide (Pd3Co/NG) nanocomposite. Rotating ring-disk electrode (RRDE) studies for the electrochemical activity towards ORR indicates that ORR proceeds via nearly four-electron mechanism. Besides, the mass activity of Pd3Co/NG shows an enhancement of 1.6 times compared to that of Pd/NG. The full fuel cell measurements were carried out using Pd3Co/NG at the anode, cathode in conjunction with Pt/C and simultaneously at both anode and cathode. A maximum power density of 68 mW/cm2 is accomplished from the simultaneous use of Pd3Co/NG as both anode and cathode electrocatalyst with individual loading of 0.5 mg/cm2 at 60 °C without any backpressure. To the best of our knowledge, the present study is the first of its kind of a fully non-Pt based PEM full cell.

Ultrafine Bimetallic PdCo Alloy Nanoparticles on Hollow Carbon Capsules: An Efficient Heterogeneous Catalyst for Transfer Hydrogenation of Carbonyl Compounds

Monodispersed ultrafine bimetallic palladium–cobalt alloy nanoparticles (PdxCoy) are prepared and immobilized on hollow carbon capsules (HCCs). Studies on the effect of metal composition on the catalytic activity of the PdxCoy reveal that the nanoparticulate alloy with the atomic composition of Pd36Co64 is more active than the Co and Pd monometallic nanoparticles in the transfer hydrogenation of carbonyl compounds. The composition of the catalyst and its alloy formation are extensively characterized, and a variety of ketones and aldehydes are hydrogenated successfully with excellent yield and high turnover number (TON), displaying the ability of the synthesized ultrafine Pd36Co64 bimetallic nanoalloy to attain and retain both high catalytic activity and stability. This catalytic system is heterogeneous, stable and does not require additives for activation. Other advantages include milder reaction conditions (does not use gaseous hydrogen), low metal content (0.17 mol %) for a catalytic transfer hydrogenat...

Palladium Cobalt Alloy Catalyst Nanoparticles Facilitated Enhanced Hydrogen Storage Performance of Graphitic Carbon Nitride

Development of a competent hydrogen storage material is the foremost task to produce the hydrogen economy feasible. In this work, nitrogen rich porous graphitic carbon nitride (g-C3N4) is decorated with palladium–cobalt alloy nanoparticles through a simple cost-effective synthesis method. It is shown, from the solid-hydrogen gas interaction studies, that Pd3Co/g-C3N4 has a room temperature hydrogen uptake capacity of 5.3 ± 0.1 wt % at 3 MPa pressure irrespective of its small surface area. Through the perfect alloying of cobalt with palladium in the g-C3N4 matrix, the synergic interaction of Pd3Co catalyst centers with g-C3N4 support material is increased by an efficient hydrogen spillover, which has improved the hydrogen uptake capacity of pristine g-C3N4 by about 65%.

Catalytic Oxidation of Hydroquinone in Aqueous Solution over Bimetallic PdCo Catalyst Supported on Carbon: Effect of Interferents and Electrochemical Measurement.

Palladium-cobalt alloy nanoparticles were synthesized and dispersed on carbon black support, aiming to have a less expensive catalyst. Catalytic behaviors of PdCo/C catalyst for the oxidation of hydroquinone (HQ) with H2O2 in aqueous solution were evaluated using high-performance liquid chromatography (HPLC). The results revealed that PdCo/C catalyst had better catalytic activity than an equal amount of commercial Pd/C and Co/C catalysts because of the d-band hybridization between Pd and Co. The effects of pH value, solvent, and various interferents including inorganic and organic compounds on the efficiency of HQ oxidation were further investigated. Furthermore, on the basis of mixed potential theory, comprehensive electrochemical measurements such as the open-circuit potential-time (OCP-t) technique and Tafel plot were efficient to assess the catalytic activity of the catalyst, and the results obtained were consistent with those of HPLC measurements. The efficient HQ oxidation was closely associated with the catalytic activity of PdCo nanoparticles because they accelerated the electron-transfer process and facilitated the generation of OH radicals.

Monodispersed palladium–cobalt alloy nanoparticles assembled on poly(N-vinyl-pyrrolidone) (PVP) as a highly effective catalyst for dimethylamine borane (DMAB) dehydrocoupling

Monodispersed PdCo@PVP NPs showed record catalytic activity, giving the best catalytic performance yet with a very high turnover frequency.

Adhesion characteristics of Staphylococcus aureus bacterial cells on funnel-shaped palladium–cobalt alloy nanostructures

ABSTRACTThe adhesion properties of Staphylococcus aureus on palladium–cobalt (Pd–Co) alloy nanostructures with various cross-sectional geometries have been characterised. They include solid core, hollow, c-shaped, and x-shaped pillars. These pillars have unique funnel-shaped geometric features on the top surfaces with average included angles between ∼142o and ∼149o. The success rates of cell attachment on these pillar tops were quantified by using field emission scanning electron microscopy techniques. Results show the Staphylococcus aureus attachment rates of Pd–Co solid core, hollow, and x-shaped pillars are statistically indistinguishable with success rate up to 82%. X-shaped pillars have the lowest attachment rate among the four geometries of 46 ± 5%.

An Effective PdCo/PWA-C Anode Catalyst for Direct Formic Acid Fuel Cells

Activated carbon was modified with phosphotungstic acid (PWA) by impregnation. Palladium-cobalt (PdCo) alloy nanoparticles were loaded on the hybrid supports (PWA-C) to prepare PdCo/PWA-C catalyst by liquid reduction method. Uniformly dispersed catalyst nanoparticles were prepared and their average particle sizes are in the range of 3.0–5.0 nm. Electrochemical measurements demonstrated that the activity of the PdCo/PWA-C catalyst was enhanced than home made Pd/C catalyst as a factor of 2.16 for formic acid oxidation. A negative shift (66 mV lower than Pd/C) of the CO stripping current peak and improved stability (5.28 times higher than Pd/C) were observed for the PdCo/PWA-C catalyst. The amount of decomposed formic acid over the PdCo/PWA-C catalyst is only 36% of the Pd/C catalyst, which indicated the excellent inhibition performance of the decomposition of formic acid for the PdCo/PWA-C catalyst. In addition, faster charge-transfer kinetics of the formic acid oxidation for the PdCo/PWA-C catalyst was found through Tafel slope measurements. The better electrocatalytic activity and stability of PdCo/PWA-C catalyst may be attributed to the synergistic effect of the PWA modification and Co alloying.

Crystalline palladium–cobalt alloy nanoassemblies with enhanced activity and stability for the formic acid oxidation reaction

In this work, we conveniently synthesize the three-dimensionally (3D) networks-like palladium–cobalt alloy nanoassemblies (Pd–Co ANAs) through a simple simultaneous reduction reaction with sodium borohydride using inorganic K2PdCl4/K3Co(CN)6 cyanogel as reaction precursors, and clarify the formation mechanism of 3D networks structure and generation mechanism of Pd–Co alloy at room temperature. The morphology, structure, size and composition of the Pd–Co ANAs are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry, chronoamperometry and CO-stripping voltammetry tests demonstrate the Pd–Co ANAs have higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning over single-component Pd nanoparticles for the formic acid oxidation reaction (FAOR) owing to their unique 3D structure and alloy property.

Low-temperature graphene growth using epochal catalyst of PdCo alloy

Palladium-Cobalt alloy as a catalyst was introduced to realize low temperature graphene growth on glass substrate by using remote RF plasma-enhanced chemical vapor deposition. Few layer graphene films were easily formed with high transmittance of 88.8% at temperature as low as 400 °C, in good contrast with Ni catalyst in which no graphitic layer was formed at all at the same conditions. High decomposition rate of hydrocarbon gases and formation of nanosize aggregates giving rise to enhancement of carbon incorporation into PdCo alloy and consequently formation of graphene layers at such low temperatures are further discussed with observed Raman spectroscopy and x-ray diffraction.

Surface micromachined metallic microneedles

In this paper, a method for fabricating surface micromachined, hollow, metallic microneedles is described. Single microneedle and multiple microneedle arrays with process enabled features such as complex tip geometries, micro barbs, mechanical penetration stops and multiple fluid output ports were fabricated, packaged and characterized. The microneedles were fabricated using electroplated metals including palladium, palladium-cobalt alloys and nickel as structural materials. The microneedles were 200 mm-2.0 cm in length with a cross-section of 70-200 /spl mu/m in width and 75-120 /spl mu/m in height, with a wall thickness of 30-35 /spl mu/m. The microneedle arrays were typically 9.0 mm in width and 3.0 mm in height with between 3 and 17 needles per array. Using water as the fluid medium, the average inlet pressure was found to be 30.0 KPa for a flow rate of 1000 /spl mu/L/h and 106 KPa for a flow rate 4000 /spl mu/L/h.