Fe Pd Research Articles

Phase stability and physical behaviour of Fe3Pd, FePd and FePd3 binary intermetallic compounds

The FP-LAPW method is used to examine the physical properties of Fe–Pd binary intermetallic compounds. The calculated formation enthalpies indicate that FePd and FePd3 compounds are thermodynamically stable in L10 and L12 phases, respectively, and the ferromagnetic Fe3Pd can be formed in a tetragonal Z1 structure with a small negative formation enthalpy. The elastic coefficients and their related parameters show that all compounds are mechanically stable and ductile in nature. The FePd-L10 is the harder compound and Fe3Pd-Z1 exhibits the highest anisotropy. The band structure, the TDOS profile and the charge density distribution show that these compounds are ferromagnetic with a metallic character and covalent-metallic bonds. The PDOS shows that the Pd-4d and Fe-3d states are dominant, and the asymmetry of Fe-3d states is behind the system strong spin polarization. The calculated magnetic moments agree well with previous theoretical results. The thermodynamic parameters are determined using the quasi-harmonic Debye model.

Synthesis and catalytic activity of porous Fe–Pd alloys in the decomposition of C2–C4 hydrocarbons

Synthesis and catalytic activity of porous Fe–Pd alloys in the decomposition of C2–C4 hydrocarbons

Iron–palladium nanoparticle biocomposites with increased metal loading

Biocomposites containing magnetic nanoparticles have the potential to combine the unique, tunable properties of nanoparticles with the strong mechanical and environmentally sustainable properties of natural fibers like cotton. Recently, a method to synthesize Fe–Pd nanoparticles on cellulose has been developed. This study presents a detailed investigation on how the structural and magnetic properties of these nanoparticle biocomposite materials are affected by increasing metal loading with respect to the cellulose while maintaining a fixed 1:1 Fe:Pd atomic ratio. Infrared spectroscopy and electron microscopy (SEM and TEM) indicate that spherical Fe–Pd nanoparticles (approximately 3–8 nm in diameter) are distributed heterogeneously throughout the fiber matrix along with amorphous iron oxide, while XRD suggests the dominant crystalline phase within the nanoparticles is likely FePd3 under significant strain. The magnetic response of the biocomposites in static and dynamic magnetic fields (as a function of frequency and temperature) reveals a polydisperse ensemble of Fe–Pd nanoparticles with up to four distributions of blocking temperatures. The lower temperature distributions are prevalent at low metal loading. As the metal loading increases, the higher temperature distributions emerge, while the lower temperature distributions are suppressed. This result points towards enhanced nanoparticle heterogeneity and agglomeration as the metal loading increases.

Fe–Pd nanoflakes decorated on leached graphite disks for both methanol and formic acid electrooxidation with excellent electrocatalytic performance

This paper introduces a unique and simple method for fabricating of inexpensive electrocatalysts for use in direct methanol fuel cells. The leached Fe1–Pd1 NFs/graphite (leached Fe1–Pd1/graphite) disk electrode was successfully obtained via uniform dispersion of Zn powder into the matrix of commercial graphite powder (98%), pressing under optimized pressure followed by the treatment in H2SO4 solution containing Fe+2 and Pd+2 cations, leading to the partial leaching out of Zn from graphite matrix, as well as partial electroless substitution of Fe–Pd nanoflakes with Zn metal. Based on the morphology studies, binary Fe–Pd nanoflakes with a large surface area uniformly dispersed on the leached graphite disk. The leached Fe–Pd/G disk showed the exceptional electrocatalytic activity toward methanol and formic acid oxidation without electrocatalyst poisoning being observed, in contrast to the leached Pd/graphite and leached Fe/graphite disks. This is due to the high surface area, and synergistic effect of Pd and Fe. The findings of this work may be used for the mass manufacture of graphite-based disks for commercial fuel cell applications using available graphite powders. The linear range of washed Fe1–Pd1/G electrocatalyst for measuring methanol was about 0.1–1.3 M, and its detection limit was calculated at about 0.03 M. Furthermore, the linear range of the nanocatalyst for measuring formic acid was about 0.02–0.1 M, and its detection limit was calculated at about 0.006 M.

Size effect for exchange interactions within Fe–Pd nanoparticles

Size effect for exchange interactions within Fe–Pd nanoparticles

Efficient separation and recovery process of Pd(II) based on sintering-leaching method by silica-based aluminum hexacyanoferrate

In the present work, several hexacyanoferrates (K2CoFe(CN)6, KAlFe(CN)6 and K2NiFe(CN)6) were theoretically analyzed based on density functional theory (DFT). Their stable structures and adsorption capabilities were compared. A silica-based hexacyanoferrate (KAlFe(CN)6/SiO2) was selected and synthesized for Pd(II) separation and recovery process. Its estimated mode particle size was 67 μm, and its average crystal size was 18.8 nm. The Fe 2p and Pd 3 d X-ray photo-electron spectra (XPS) of Pd-loaded KAlFe(CN)6/SiO2 and density functional theory calculation revealed that the adsorption mechanism is the spontaneous displacement of K+ by Pd2+. A novel sintering-leaching method was developed for the recovery of Pd(II) from spent adsorbent. The effects of different sintering times, leaching temperatures, and leaching media were investigated, indicating that the optimal condition (sintering at 400 °C for 24 h, leaching in 3 M HCl at 50 °C) could reach a Pd(II) recover ratio of 88%. Energy-dispersive spectroscopy (EDS) and XPS tests were performed on the leaching product, and the results confirmed that the recovered product was PdO with purity of 91.8%.

Poly-icosahedral Co–Fe–Pd nanoalloy: Isomerism effect on the structural and magnetic properties from DFT

This study seeks to understand and explain the role of isomerism on the structural and magnetic properties of Co–Fe–Pd nanoalloys. To this end, semiempirical Gupta potential was utilized to identify the first three isomers and the global minimum structures of all compositions, and then these isomers were subject to re-optimization by means of the DFT approach. The structural analysis of Co2FenPd17-n (n = 0–17) nanoalloys revealed that Co atoms prefer locations in the inner sites of the nanoalloys. Fe and Pd atoms occupy the surface for both GM structures and isomers. Our general result shows an increase in the total magnetic moment of the nanoalloys but a decrease in the local magnetic moments of the Co and Fe atoms. Another important result is that the local magnetic moment of the Pd atoms is not zero. These results support the idea that the isomerism effect plays a crucial role in structural and magnetic properties.

Bimetallic Intersection in PdFe@FeOx‐C Nanomaterial for Enhanced Water Splitting Electrocatalysis

AbstractSupported Fe‐doped Pd‐nanoparticles (NPs) are prepared via soft transformation of a PdFe‐metal oraganic framework (MOF). The thus synthesized bimetallic PdFe‐NPs are supported on FeOx@C layers, which are essential for developing well‐defined and distributed small NPs, 2.3 nm with 35% metal loading. They are used as bifunctional nanocatalysts for the electrocatalytic water splitting process. They display superior mass activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), both in alkaline and acid media, compared with those obtained for benchmarking platinum HER catalyst, and ruthenium, and iridium oxide OER catalysts. PdFe‐NPs also exhibit outstanding stability against sintering that can be explained by the protecting role of graphitic carbon layers provided by the organic linker of the MOF. Additionally, the superior electrocatalytic performance of the bimetallic PdFe‐NPs compared with those of monometallic Pd/C NPs and FeOx points to a synergetic effect induced by Fe–Pd interactions that facilitates the water splitting reaction. This is supported by additional characterization of the PdFe‐NPs prior and post electrolysis by TEM, XRD, X‐ray photoelectron spectroscopy, and Raman revealing that dispersed PdFe NPs on FeOx@C promote interactions between Pd and Fe, most likely to be Pd–O–Fe active centers.

Morphological and Structural Transformations of Fe-Pd Powder Alloys Formed by Galvanic Replacement, Annealing and Acid Treatment.

In this article, we report the preparation and structural features of Fe-Pd powder alloys formed by galvanic replacement, annealing and selective dissolution of iron via acid treatment. The alloys were studied by the X-ray diffraction phase analysis, Mössbauer spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The Fe@Pd core–shell particles were obtained by a galvanic replacement reaction occurring upon treatment of a body-centered cubic (bcc) iron powder by a solution containing PdCl42− ions. It was found that the shells are a face-centered cubic (fcc) Pd(Fe) solid solution. HCl acid treatment of the Fe@Pd core–shell particles resulted in the formation of hollow Pd-based particles, as the bcc phase was selectively dissolved from the cores. Annealing of the Fe@Pd core–shell particles at 800 °C led to the formation of fcc Fe-Pd solid solution. Acid treatment of the Fe-Pd alloys formed by annealing of the core–shell particles allowed selectively dissolving iron from the bcc Fe-based phase (Fe(Pd) solid solution), while the fcc Fe-rich Fe-Pd solid solution remained stable (resistant to acid corrosion). It was demonstrated that the phase composition and the Fe/Pd ratio in the alloys (phases) can be tailored by applying annealing and/or acid treatment to the as-synthesized Fe@Pd core–shell particles.

Disordered to ordered phase transformation: Correlation between microstructure and magnetic properties in Fe–Pd thin films

The kinetics of the transformation from the disordered to the ordered phase has been studied in Fe56Pd44 thin films deposited on silicon substrates by Joule evaporation. Subsequent thermal treatments at 550 °C in vacuum were performed at different annealing times to promote the formation and the optimization of the ordered L10 FePd phase. X-ray diffraction allowed us to investigate the microstructure of the samples (grain size, volume fraction of the transformed phase, order parameter of the ordered phase, and average order of the alloy), whereas magnetic measurements allowed us to evaluate coercivity and to independently estimate the volume fraction of the ordered L10 phase. The kinetics of the transformation turned out to reach completion after 20 min of annealing time with the grain size growing with a power law with an exponent equal to 8.24. The resulting monophasic film has a high density of defects, which contribute to the magnetic coercivity. A linear relationship between the coercive field and the average order parameter of the alloy has been established. Finally, the evolution of the transformed phase obeys Avrami's law with an exponent of ∼0.4, indicating that the transformation is controlled by the nucleation mechanism without grain growth.

Computational screening of spinel structure cathodes for Li-ion battery with low expansion and rapid ion kinetics

Lithium ion batteries (LIBs) dominate the market of energy storage systems due to their high energy density and light weight. Spinels, a group of environmentally friendly, low cost and thermal stable materials, have been reported as high-performance cathode candidates of LIBs. In spinel LIBs, Mn-based spinels (LiMnO4) have been widely studied, and further reports have been carried out on the doping of LiMnO4 structures to suppress the disproportionation reaction of the Mn3+. However, the application of spinel cathodes in LIBs is still affected by the volume expansions and slow ion diffusion kinetics. In this work, we generated 62 spinel materials from the periodic table based on the widely studied LiB2X4 and LiMn1.5B0.5X4 structures (i.e., Mn-based spinel with doping of elements B), where the element B can be chosen from the Co, Cr Fe Ir, Mn, Mo, Ni, Pd, Pr, Rh, Ti, V, Ce, Tb, Ru or Ta while the element X can be an anion of O or S. Based on the density functional theory (DFT), the electronic conductivities, expansion coefficients and ion kinetics of the selected 62 spinel structures were predicted. Finally, we screened out 18 structures having excellent electronic conductivity (i.e., the band gap, Eg = 0), low expansion coefficient (<10%) and low diffusion energy barrier (<0.4 eV). In addition, 8 spinel structures were found to be superionic conductor with extremely high ionic conductivity (>10−4 S·cm−1). The proposed work not only filtered out the spinel electrode materials with the best performance for LIBs and found the superionic conductor based on lithium spinel, but also provided an efficient solution for the search of other excellent electrode materials with optimal structures.

Enhanced adsorption and reduction performance of nitrate by Fe–Pd–Fe3O4 embedded multi-walled carbon nanotubes

Multi walled carbon nanotubes (MWCNTs) have attracted more and more attention as adsorbents due to their excellent adsorption properties. By loading metal particles on MWCNTs, the chemical reduction ability of adsorbed pollutants could be provided, so as to achieve the purpose of adsorption and degradation of pollutants. Therefore, the removal process of NO3−-N by Fe–Pd–Fe3O4/MWCNTs was studied, including rapid adsorption of initial pollutants, gradual reduction of intermediate products and re-adsorption of final products. The results showed that Fe–Pd–Fe3O4/MWCNTs completely removed NO3−-N within 2 h, 39% and 25% of which were converted into NO2−-N and NH4+-N. The adsorption efficiency, kinetics, capacity and adsorption energy all followed the order of NH4+-N > NO2−-N > NO3−-N. With the recoverability and reusability of Fe–Pd–Fe3O4/MWCNTs having been confirmed in 5 consecutive cycles, the removal rate of NO3−-N still reached 43%. It has been shown that MWCNTs prolonged the reducing power for NO3−-N, due to avoiding the aggregation of metal particles. The rapid adsorption of initial pollutants, effective stepwise reduction and convenient recovery processes were of great value for the rehabilitation of polluted water.

Thickness-dependent L10 ordering behavior in polycrystalline Fe–Pd nanoparticle films on glass substrates

The dependence of the L10 ordering, magnetic properties and microstructure on film thickness of the Fe51Pd49 nanoparticle films deposited at 800 °C was investigated. The L10 ordered phase and hard magnetic properties were found for the samples with the thickness less than 30 nm. As the thickness was increased to 45 nm and thicker, the samples exhibited the A1 disordered phase and soft magnetic properties. The lack of heterogeneous nucleation sites is responsible for the A1 disordered phase in the thicker FePd samples, which was confirmed by the results of microstructural and crystallographic analyses. The long term re-annealing at a lower temperature (600 °C for 8 h) can induce the L10 ordering of the large size FePd nanoparticles originally composed of the A1 phase, which also supports the statement that the heterogeneous nucleation sites play an important role on L10 ordering of the FePd films.

Structural, magnetic and magnetostrictive properties of the ternary iron–palladium–silicon ferromagnetic shape memory ribbons

The influence of the partial substitution of Fe by Si and thermal treatments on the structural, magnetic and magnetostrictive properties of the Fe67.5Pd30.5Si2 rapidly solidified ribbons has been investigated. A remarkable decrease in the martensite transformation temperature, with ~ 65 K lower than that of the Fe–Pd archetype alloy, is observed in the as-prepared ribbons. The thermal treatments shift the martensite transformation temperatures upward, with approximately 13 K for the higher thermal treatment. Also, these induce an improvement in the crystallinity in these ribbons with high texture and an increase in the crystallite size as a result of reducing the internal defects and stress. The thermodynamic considerations discussed in the frame of the Clapeyron–Clausius relation by using the calorimetric and thermomagnetic measurements (up to 7 T) reveal a weak influence of the magnetic fields on the martensitic transformation temperatures (~ 0.5 K/T). The magnetostriction decrease with temperature under small magnetic fields was discussed, beside an unusual behaviour in the technically saturated domain. This behaviour is based on the coexistence of the ordinary and forced magnetostrictions, the last one increasing faster with the temperature decreasing.

Impacts of atomic and magnetic configurations on the phase stability of Fe–Pd shape memory alloys: A first-principles study

The effects of local atomic and magnetic configurations on the phase stability and elastic property of the face-centered cubic (fcc) and two body-centered tetragonal [face-centered tetragonal (fctI) and fctII, with 0.9&amp;lt;c/a&amp;lt;1 and 0.71&amp;lt;c/a&amp;lt;0.9, respectively, in the fct unit cell] phases of Fe1−xPdx (0.28≤x≤0.34) shape memory alloys are systematically investigated by using the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation. It is shown that, considering four types of atomic configurations in a fcc unit cell, the two with one random sublattice are both preferable in each x below 300 K. When T=300 K, the one with three random sublattices also changes to be stabilized for x≤0.30, whereas that with four random sublattices becomes stable in most of these alloys until T≥600K. Upon tetragonal distortions, in these fully disordered alloys, both the fctI and fctII phases are unstable. The fctI phase is found for 0.29≤x≤0.33, having only the configuration with one random sublattice on the same layer with the Pd site in the unit cell, whereas the fctII phase is obtained for x≤0.30, possessing all the configurations with one, two, and three random sublattices. These results representing the phase diagram of these alloys, their determined equilibrium lattice parameters, and elastic constants of the three phases at 0 K are in line with the experimental and theoretical data, and their estimated structural (TM) and magnetic (TC) transition temperatures are also close to the experimental data. Adding 4% magnetic disorder in Fe0.70Pd0.30, the fctII structure is effectively prevented, whereas the thermoelastic martensitic transformation of fcc–fctI can still be retained at 0 K.

Synthesis of an Fe–Pd bimetallic catalyst for N-alkylation of amines with alcohols via a hydrogen auto-transfer methodology

A bimetallic catalyst, Fe10Pd1/NC500, was prepared, and it efficiently catalyzed the N-alkylation of amines with alcohols due to the synergistic effects inside.

Dependence of the Magnetization Process on the Thickness of Fe70Pd30 Nanostructured Thin Film.

Fe–Pd magnetic shape-memory alloys are of major importance for microsystem applications due to their magnetically driven large reversible strains under moderate stresses. In this context, we focus on the synthesis of nanostructured Fe70Pd30 shape-memory alloy antidot array thin films with different layer thicknesses in the range from 20 nm to 80 nm, deposited onto nanostructured alumina membranes. A significant change in the magnetization process of nanostructured samples was detected by varying the layer thickness. The in-plane coercivity for the antidot array samples increased with decreasing layer thickness, whereas for non-patterned films the coercive field decreased. Anomalous coercivity dependence with temperature was detected for thinner antidot array samples, observing a critical temperature at which the in-plane coercivity behavior changed. A significant reduction in the Curie temperature for antidot samples with thinner layer thicknesses was observed. We attribute these effects to complex magnetization reversal processes and the three-dimensional magnetization profile induced by the nanoholes. These findings could be of major interest in the development of novel magnetic sensors and thermo-magnetic recording patterned media based on template-assisted deposition techniques.

Thermoresponsive PNIPAm–PMMA-Functionalized PVDF Membranes with Reactive Fe–Pd Nanoparticles for PCB Degradation

Fe–Pd nanoparticles are immobilized in stimuli-responsive poly-N-isopropylacrylamide (PNIPAm)- and poly-methyl methacrylate-functionalized polyvinylidene fluoride membranes using ion exchange for 2...

Enhancements in catalytic activity and duration of PdFe bimetallic catalysts and their use in direct formic acid fuel cells

The palladium–iron based bimetallic catalysts (PdxFey/Cs) and facile synthetic method are introduced to enhance the catalytic activity and operational duration for direct formic acid fuel cells. To improve the properties of PdxFey/C catalysts, such as degree of PdFe alloy and its crystallinity, heat treatment is conducted at 600°C. According to results, the Pd–Fe bond and Fe metal particle are formed after the heat treatment, while iron oxides and Pd particles are observed in the untreated samples. Electrochemical evaluations for measuring the formic acid oxidation reaction rate demonstrates heat treated Pd3Fe1/C (HT-Pd3Fe1/C) is the best catalysts of six samples which are synthesized by using different Pd to Fe ratios (3:1, 1:1, 1:3) before and after heat treatment. This is because the HT-Pd3Fe1/C has high Pd–Fe alloying and Pd contents. Through the heat treatment, the indirect formic acid oxidation reaction way is activated and the resistance to CO poisoning is significantly improved. The maximum power density of direct formic acid fuel cells using HT-Pd3Fe1/C whose open circuit voltage is 0.83V is 137mWcm−2, which is 1.6 and 1.9 times higher than that of direct formic acid fuel cells using untreated catalyst and Pd/C.

Unusual behavior of bimetallic nanoparticles in catalytic processes of hydrogenation and selective oxidation

Abstract Recent results obtained in studying mono- and bimetallic catalysts for selective hydrogenation of unsaturated carbonyl compounds, even unsaturated ones, acetylenic and nitro compounds as well as CO and bio-available alcohols oxidation are reviewed from the standpoint of the strong interaction between the metal nanoparticles, on the one hand, and two metals in the composition of bimetallic nanoparticles, on the other hand. Such interactions were demonstrated to result in partial positive or negative charging of metal nanoparticles, which, in turn, changes their adsorption and catalytic properties, especially with respect to the reactions involving hydrogen. Among the systems studied, Au–Pt, Au–Pd, Au–Cu, Au–Fe, Pt–WO x , Fe–Pd, Fe–Pt, Fe–Cu nanoparticles prepared by the redox procedure are considered to be most perspective in diverse catalytic applications because of the proper combination of the particle size and the electronic state of the metals.