PdCu Alloy Research Articles

The factors affecting the diffusion properties of hydrogen in palladium copper alloys: Ab initio study

The experiments showed that the addition of copper (Cu) in palladium (Pd) membrane reduces the permeability of hydrogen (H) in Pd, and the permeability of H in body-centered cubic (BCC) PdCu alloy is larger than that in face-centered cubic (FCC) PdCu alloy. The underlying reasons are still not well understood. In the present work, systematical ab initio calculations are carried out to investigate the factors affecting the diffusion properties of H in PdCu alloys. It is found that the lowest diffusion barrier of H with zero-point energy correction in BCC PdCu alloy (0.016 eV) is relatively low than that in FCC PdCu alloy (0.346 eV). The interactions among interstitial H atoms are significantly repulsive in BCC PdCu alloy, while it is attractive in FCC PdCu alloy. The results suggest that it is energetically favorable to form interstitial H cluster in FCC PdCu alloy rather than that in BCC PdCu alloy. The formation of interstitial H clusters impedes the fast movement of H in FCC PdCu alloy. The presence of intrinsic vacancy in FCC PdCu alloy further hinders the migration of H. It is found that the binding strength of vacancy with H in FCC PdCu alloy is much larger than that in BCC PdCu. The stronger the combination of H and vacancy, the greater the obstacle to the movement of H in PdCu alloy. All these results elucidate the experimental phenomena why H penetration ability in FCC PdCu alloy is weaker than that in BCC PdCu alloy.

A modified elastic constant calculation method for triclinic-like special quasi-random structures: Application to Pd-M (M = Cu, Ag) solid solutions

The mechanical properties of Palladium alloys need to be calculated using first principles due to high experiment cost. For FCC disordered Pd alloys, special quasi-random structure (SQS) is usually used for modeling at first and the calculation of mechanical properties usually begins with elastic constants. However, SQS supercells are often triclinic-like and show lower symmetry than origin FCC structure, which would lead to the elements of elastic matrix calculated by DFT aren’t equal to elastic constants. To solve this problem, a strain operation method is put forward by linear transformation, LSQS′=SDL, to modify energy-strain method. Taking Pd-M (M = Cu, Ag) random alloys as an application case, the elastic properties of Pd-Cu and Pd-Ag alloys with 5 at% concentration gradient are calculated. The calculation results are similar to experiment data and other DFT works, which indicate that the preceding formula is valid. Electron structure analysis shows that Pd valence electrons are the main contributors to metallic bonds.

Selective Alkyne Semi‐Hydrogenation by PdCu Nanoparticles Immobilized on Stereocomplexed Poly(lactic acid)

AbstractPolymer‐supported PdCu alloy nanoparticles with a palladium to copper atom ratio of 1 have been synthesized upon: (i) Coordination of palladium/copper acetate to 2,2’‐bipyridine‐end functionalized poly(lactic acid) (PLA); (ii) Stereocomplexation of PLA‐based macrocomplexes of opposite stereochemistry, and (iii) metal reduction with hydrogen. The obtained supported PdCu nanoparticles were successfully applied in the semi‐hydrogenation of industrially important alkynols, such as 3‐hexyn‐1‐ol and 2‐butyne‐1,4‐diol leading to the corresponding cis‐alkenol in high selectivity (98 %) under mild reaction conditions (i. e. ethanol, T (25 °C), p(H2)=3 bar) in the absence of any further additive. From a comparison of the catalytic performance of supported PdCu nanoparticles with those of Pd and Cu, located in the same chemical environment, emerged a clear alloy effect (i. e. high chemoselectivity for the alkene at high alkyne conversion). Recycling experiments conducted with the PdCu‐based catalyst proved the stability of the catalyst with time, even by its recovering in air atmosphere.

Alloyed PdCu Nanoparticles within Siliceous Zeolite Crystals for Catalytic Semihydrogenation.

Selective hydrogenation of acetylene to ethylene is an industrially important process to purify the raw ethylene stream for producing high-grade polyethylene. The supported Pd catalyst exhibits superior activity for acetylene hydrogenation but suffers from poor ethylene selectivity because of the easy overhydrogenation to produce ethane. Here, we report that the PdCu alloy nanoparticles within siliceous zeolite crystals effectively tuned Pd-catalyzed overhydrogenation into semihydrogenation. This catalyst displayed an ethylene selectivity of 92.9% with a full conversion of acetylene. Mechanism studies reveal that the zeolite fixation stabilized the alloyed structure, where the electron-enriched Pd surface benefits the rapid ethylene desorption to hinder the deep hydrogenation. This work provides an efficient strategy for a rational design of bimetallic metal catalysts for selective hydrogenations.

Electrocatalytic nitrate reduction on bimetallic Palladium-Copper Nanowires: Key surface structure for selective dinitrogen formation

Selective electrocatalytic nitrate reduction reaction (NO3RR) to dinitrogen (N2) is essential to nitrogen-cycle management and environmental sustainability. Palladium-based nanomaterials were extensively studied as NO3RR catalysts, but only delivered limited N2 selectivity (<50%, NH3 dominated the product). Here we report that, by tuning bimetallic composition of CuPd alloy nanowires, the Cu28Pd72 nanowires deliver a near-unit conversion of NO3–-N and an unprecedented N2 product selectivity of 75.9 ± 5.2% in treating 22.5 mg L−1 NO3–-N solution at −0.80 V vs. Ag/AgCl. Combining in-situ spectrometric measurements and theoretical calculations, we demonstrate that the contiguous Pd ensemble with a specific size at catalyst surface is essential to the N2 formation via a kinetically-favored pathway of NO2* → NO* → N* → N2*. Alloying Pd with Cu is indispensable as Cu contributes to the N*-N* pairing by initiating the NO3––NO2* conversion and lowering the Hads coverage on catalyst. This work discloses the key surface atomic structure for N2 formation, and provides a guideline for the design of efficient NO3RR catalyst that enables selective NO3––N2 conversion.

Surface Nitridation of PdCu Nanosheets to Promote Charge Transfer and Suppress CO Poisoning toward Ethanol Electrooxidation

AbstractAlthough PdCu alloy is recognized as an active catalyst for ethanol electrooxidation, its activity needs significant enhancement to satisfy the practical application. In this study, surface nitrided PdCu nanosheets are constructed through a facile nitrogen plasma treatment. The obtained catalyst shows highly enhanced catalytic activity and stability toward ethanol oxidation reaction in comparison with normal PdCu nanosheets and Pd nanosheets. The improvement should be ascribed to the combined electronic and structural effects from introduced Cu and facile surface nitridation, which promote charge transfer and suppress CO poisoning. This work offers a guideline to design and synthesize efficient catalysts for energy electrocatalysis by rational surface engineering.

A Strategy to Promote the Orr Electrocatalytic Activity by the Novel Engineering Bunched Three-Dimensional Pd-Cu Alloy Aerogel

A Strategy to Promote the Orr Electrocatalytic Activity by the Novel Engineering Bunched Three-Dimensional Pd-Cu Alloy Aerogel

Fabrication of Dendritic Pdcu Alloy Supported on 3d N-Doped Hollow Graphene for Efficient Ethanol Electro-Oxidation

Fabrication of Dendritic Pdcu Alloy Supported on 3d N-Doped Hollow Graphene for Efficient Ethanol Electro-Oxidation

A Novel Mof-Derived Strategy to Construct Cu-Doped Ceo2 Supported Pdcu Alloy Electrocatalysts for Hydrogen Evolution Reaction

A Novel Mof-Derived Strategy to Construct Cu-Doped Ceo2 Supported Pdcu Alloy Electrocatalysts for Hydrogen Evolution Reaction

Long-life reversible Li-CO2batteries with optimized Li2CO3flakes as discharge products on palladium-copper nanoparticles

A long-life Li-CO2battery was achieved with bimetallic PdCu alloys on CNFs as a cathode.

Investigation of glycerol electrooxidation activity of carbon supported PdCu bimetallic electrocatalyst.

In this study, Pd/C, Cu/C, and a series of PdCu/C bimetallic electrocatalysts were prepared by microwave-assisted modified polyol method to determine glycerol electrooxidation reaction (GOR) activities. The effect of microwave duration on catalyst structure and GOR activity was investigated on PdCu/C bimetallic catalysts. Also, a commercial Pd/C (com-Pd/C) was used to compare catalytic activities with prepared samples. Electrocatalysts were characterized by using X-ray Diffraction (XRD), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and Transmission Electron Microscopy (TEM) analyses. In addition, the activity and stability of electrocatalysts for GOR were examined by using cyclic voltammetry (CV) and chronoamperometry (CA). In XRD results, the formation of PdCu alloy structure was observed successfully in all bimetallic catalysts. It was found that the PdCu electrocatalyst with microwave duration of 150 s (PdCu150) was exhibited homogeneous dispersion in TEM images. The particle size of 6.45 nm for PdCu150 was identified from TEM. Furthermore, the performance results were indicated that PdCu150 has the highest activity (36.02 mA/cm2) and stability compared to Pd/C (8.56 mA/cm2), and com-Pd/C (10.23 mA/cm2) in glycerol electrooxidation.

Precisely modulated 2D PdCu alloy nanodendrites as highly active peroxidase mimics for the elimination of biofilms.

Pd-based nanomaterials are good candidates for antibacterial applications because of their high catalytic activity and good biocompatibility. Nonetheless, there is still much work to do to improve the catalytic activity of Pd nanomaterials as antibacterial agents, particularly for anti-biofilms. In this work, Cu was introduced into Pd to form a series of 2D PdCu alloy nanodendrites (PdCu NDs) as high-performance peroxidase mimics based on flexible control of compositions. Remarkably, catalytic kinetics show that the composition-dependent synergy in the PdCu NDs strongly enhances the peroxidase-like activity. The detailed theoretical study reveals that the tuning of the electrostatic adsorption and dissociative chemisorption of the H2O2 molecule on PdCu ND surfaces by the precise introduction of Cu plays a key role in obtaining superior peroxidase-like catalytic activity. Significantly, the distinct peroxidase-like properties of the fine-tuned PdCu NDs endow them with excellent biofilm elimination capability via the generation of hydroxyl radicals. This work offers a great opportunity to design noble metal nanozymes with enhanced performance, which might advance the development of nanozymes as a new class of highly efficient antibacterial agents.

Characterization of Pd60Cu40 Composite Membrane Prepared by a Reverse Build-Up Method for Hydrogen Purification

A thin Pd-based H2-permeable membrane is required to produce high-purity H2 with high efficiency. In this study, a porous Ni-supported Pd60Cu40 composite H2-permeable membrane was developed using a reverse build-up method to produce economical H2 purification. The thickness of the Pd60Cu40 alloy layer produced by the improved membrane production process reached 1.0 μm; it was thinner than the layer obtained in a previous study (3.7 μm). The membrane was characterized by scanning electron microscope, inductively coupled plasma optical emission spectrometer, H2 permeation test, and Auger microprobe analysis. The permeation tests were performed at 300–320 °C and 50–100 kPa with H2 introduced from the primary side. The H2 permeation flux was stable up to ~320 °C. The n-value was determined to be 1.0. The H2 permeance of the membrane was 2.70 × 10−6 mol m−2 s−1 Pa−1.0 at 320 °C, after 30 h, similar to those of other 2.2-µm-thick and 3.7-µm-thick Pd60Cu40 composite membranes, suggesting that the adsorption and dissociation reaction processes on the PdCu alloy surface were rate-limiting. The Pd cost of the membrane was estimated to be ~1/30 of the Pd cost of the pure Pd60Cu40 membrane.

Chemoselective reduction of α,β-unsaturated carbonyl compounds in the presence of CuPd alloy nanoparticles decorated on mesoporous graphitic carbon nitride as highly efficient catalyst

Herein, we reported reductions of acid, amide, ester and ketone groups with selectivity (>99%) by the catalytic transfer hydrogenation of with CuPd alloy nanoparticles (NPs) decorated on mesoporous graphitic carbon nitride (Cu50Pd50/mpg-C3N4) catalyst under mild conditions in a water/methanol mixture. CuPd alloy NPs were synthesized by the co-reduction of palladium (II) acetylacetonate and copper(II) acetylacetonate in oleylamine (OAm) solution by the reduction of morpholine-borane solution and then assembled on mpg-C3N4 via liquid phase self‐assembly method. The α, β-unsaturated carbonyl compounds were obtained from the condensation reaction of the benzaldehyde derivatives with acetone derivatives. Cu50Pd50/mpg-C3N4 nanocatalyst was characterized by TEM, XRD, XPS, BET and ICP‐MS. Cu50Pd50/mpg-C3N4 nanocatalyst is highly active catalyst for the reduction of various organic groups and converted to high yield and 99% selectivity. The superior Cu50Pd50/mpg-C3N4 nanocatalyst is highly efficient and reusable catalyst which is reuse after 5 cycle with 98% conversion.

Atmosphere-Induced Transient Structural Transformations of Pd-Cu and Pt-Cu Alloy Nanocrystals.

We have investigated the transformations of colloidal Pd–Cu and Pt–Cu bimetallic alloy nanocrystals (NCs) supported on γ-Al2O3 when exposed to a sequence of oxidizing and then reducing atmospheres, in both cases at high temperature (350 °C). A combination of in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray absorption spectroscopy was employed to probe the NC surface chemistry and structural/compositional variations in response to the different test conditions. Depending on the type of noble metal in the bimetallic NCs (whether Pd or Pt), different outcomes were observed. The oxidizing treatment on Pd–Cu NCs led to the formation of a PdCuO mixed oxide and PdO along with a minor fraction of CuOx species on the support. The same treatment on Pt–Cu NCs caused a complete dealloying between Pt and Cu, forming separate Pt NCs with a minor fraction of PtO NCs and CuOx species, the latter finely dispersed on the support. The reducing treatment that followed the oxidizing treatment largely restored the Pd–Cu alloy NCs, although with a residual fraction of CuOx species remaining. Similarly, Pt–Cu NCs were partially restored but with a large fraction of CuOx species still located on the support. Our results indicate that the noble metal present in the bimetallic Cu-based alloy NCs has a strong influence on the dealloying/migrations/realloying processes occurring under typical heterogeneous catalytic reactions, elucidating the structural/compositional variations of these NCs depending on the atmospheres to which they are exposed.

Seeded Synthesis of Unconventional 2H-Phase Pd Alloy Nanomaterials for Highly Efficient Oxygen Reduction.

Crystal phase engineering of noble-metal-based alloy nanomaterials paves a new way to the rational synthesis of high-performance catalysts for various applications. However, the controlled preparation of noble-metal-based alloy nanomaterials with unconventional crystal phases still remains a great challenge due to their thermodynamically unstable nature. Herein, we develop a robust and general seeded method to synthesize PdCu alloy nanomaterials with unconventional hexagonal close-packed (hcp, 2H type) phase and also tunable Cu contents. Moreover, galvanic replacement of Cu by Pt can be further conducted to prepare unconventional trimetallic 2H-PdCuPt nanomaterials. Impressively, 2H-Pd67Cu33 nanoparticles possess a high mass activity of 0.87 A mg-1Pd at 0.9 V (vs reversible hydrogen electrode (RHE)) in electrochemical oxygen reduction reaction (ORR) under alkaline condition, which is 2.5 times that of the conventional face-centered cubic (fcc) Pd69Cu31 counterpart, revealing the important role of crystal phase on determining the ORR performance. After the incorporation of Pt, the obtained 2H-Pd71Cu22Pt7 catalyst shows a significantly enhanced mass activity of 1.92 A mg-1Pd+Pt at 0.9 V (vs RHE), which is 19.2 and 8.7 times those of commercial Pt/C and Pd/C, placing it among the best reported Pd-based ORR electrocatalysts under alkaline conditions.

Palladium-copper membrane prepared by electroless plating for hydrogen separation at low temperature

Pd-based membranes are often used to purify hydrogen, but often fail as a result of phase changes at low temperatures. In this study, an electroless plated Pd-Cu membrane was produced to purify hydrogen generated during various low temperature processes. The membrane was fabricated by sequential electroless plating of Pd and Cu with hydrazine as a reducing agent, followed by alloying in a hydrogen atmosphere. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses confirmed that the Pd-Cu layer was successfully alloyed, and thickness of the alloy layer was 23.74 µm. The hydrogen permeability of the Pd-Cu membrane prepared in this work was significantly increased compared to the previously published results. The hydrogen permeation flux of 0.6 m3 m−2 h−1 for the Pd-Cu membrane was stable over a period of 10 h at 175 °C without suffering hydrogen embrittlement and was stable over a temperature cycle. Finally, hydrogen temperature-programmed desorption (H2-TPD) confirmed that the desorption properties of hydrogen were changed by using this Pd-Cu alloy.

Amperometric Oxygen Sensor Based on Bimetallic Pd-Cu/C Electrocatalysts

A laminated Pd-Cu alloy/C/Nafion multilayer was prepared to sense O2 atmosphere in a metal-air structure. As a matrix, palladium was doped with various amounts of copper to conduct a preliminary test with optimum response, and four compositions, Pd, Pd8Cu2, Pd6Cu4, and Pd5Cu5, were selected as the candidate electrodes. It was found that the Pd6Cu4/C electrode showed higher sensitivity for all the electrodes. According to the phase identification of X-ray diffraction and X-ray photoelectron spectroscopy tests, the high sensitivity was attributed to the doped Cu, which was merged into the Pd matrix to repel the Pd out of the matrix as a Pd-skin layer on the surface. In the Pd-Cu alloy, the Cu site served as a template reaction site to break the O-O bond and reduce the interaction force of adsorbated oxygen on the Pd site. During the oxygen reduction reaction, not only did the decomposition of O2 molecules occur on the electrode, but the electrode itself proceeded with a phase transformation to high valance of oxide, PdO3. The sensing potential for O2 sensing was determined by polarization curves in which the flat region resulting from a diffusion-control was adopted. Chronoamperometric measurements were employed to construct calibration curves for the selected electrodes. A successive response was measured to test the endurance, which showed appreciable sensitivity decay. We also tested the selectivity by introducing a series of disturbance gases, CO, SO2, and NO2, in which the Pd6Cu4 electrode prevailed over the other electrodes.

Low-crystalline PdCu alloy on large-area ultrathin 2D carbon nitride nanosheets for efficient photocatalytic Suzuki coupling

We develop a new PdCu/UTCN hybrid by loading low-crystalline PdCu NPs on large-area ultrathin 2D carbon nitride (UTCN) nanosheets that exfoliated from bulk g-C3N4 using a twice thermal exfoliation and repolymerization method for photocatalytic Suzuki C-C cross coupling reaction. Due to the advantages of 2D structure of the UTCN and the changes in electronic structure and surface structure of low-crystalline PdCu NPs, PdCu/UTCN shows promoted photocatalytic activity with high selectivity for Suzuki coupling reaction. The TOF value for coupling of iodobenzene with phenylboronic acid is 418.2 h−1, which is 8 and 6.2 times higher than that of previously reported Pd-g-C3N4 and Pd based alloy photocatalysts under the same reaction, respectively. Morevoer, this photocatalyst shows a good functional group tolerance as well as good to excellent yield and selectivity for various substrates. This study reports for the first time the PdCu alloy supported UTCN photocatalytic material for enhanced Suzuki reaction.

Alloying effect-induced electron polarization drives nitrate electroreduction to ammonia

Electrocatalytic conversion of nitrate (NO 3 − ) to ammonia (NH 3 ) holds significant potential in the control of nitrogen oxide (NO x ) from stationary sources. However, previous studies on reaction intermediates remain unclear. Here we report that PdCu/Cu 2 O hybrids with mesoporous hollow sphere structure show high selectivity (96.70%) and Faradaic efficiency (94.32%) for NH 3 synthesis from NO 3 − . Detailed characterizations demonstrate that (1) Pd enables electron transfer (Pd 3d → Cu 3d) and causes the polarization of Cu 3d orbitals by forming partial PdCu alloys, which makes Pd electron deficient but offers empty orbits to adsorb NO 3 − , and (2) electron-rich Cu is more conducive to the occurrence of NO 3 − reduction. The mutual confirmation of online differential electrochemical mass spectrometry and density functional theory calculations demonstrates that PdCu alloys block the generation of ∗NOH intermediate and facilitate the formation of ∗N, providing a new mechanism for NH 3 synthesis from NO 3 − reduction reactions. • PdCu/Cu 2 O hybrids with alloying effect for electrocatalytic NH 3 synthesis • Pd causes the polarization of Cu 3d orbitals by forming partial PdCu alloys • PdCu alloys facilitate the formation of ∗N intermediates for better NH 3 synthesis The reduction treatment of NO x by traditional methods is conducted at high temperature (>400°C), and this process requires considerable energy. Our approach is to convert NO x into NO 3 − in solution by an oxidation and leaching absorption process and subsequently effectively convert NO 3 − into value-added NH 3 (a hydrogen source and a fertilizer). Electrocatalytic reduction of NO 3 − to NH 3 holds important potential in the control of NO x . However, previous studies have not been involved in the regulation of intermediates. By depositing Pd species on Cu 2 O, we achieved significantly improved NH 3 synthesis performance. Pd species make Cu 3d orbitals easier to polarize and act as new adsorption sites instead of Cu 2 O. Detailed characterizations demonstrate that highly dispersed PdCu alloys formed by the deposition of Pd 0 on Cu 2 O can tune the original NH 3 synthesis path of Cu 2 O by facilitating the formation of the ∗N intermediate, ultimately leading to a higher selectivity and Faradaic efficiency. PdCu/Cu 2 O hybrids with a mesoporous hollow sphere structure can efficiently synthesize NH 3 . Pd species make Cu 3d orbitals easier to polarize and act as new adsorption sites of NO 3 − instead of Cu 2 O. The highly dispersed PdCu alloys can efficiently facilitate the formation of ∗N and block the generation of the ∗NOH intermediate, leading to a remarkable selectivity toward NH 3 and Faradaic efficiency. This work highlights a promising route to design Cu 2 O hybrids for selective electrocatalytic NH 3 synthesis to control NO x emission.