Clean Synthesis of an Economical 3D Nanochain Network of PdCu Alloy with Enhanced Electrocatalytic Performance towards Ethanol Oxidation

A one‐pot method for the fast synthesis of a 3D nanochain network (NNC) of PdCu alloy without any surfactants is described. The composition of the as‐prepared PdCu alloy catalysts can be precisely controlled by changing the precursor ratio of Pd to Cu. First, the Cu content changes the electronic structure of Pd in the 3D NNC of PdCu alloy. Second, the 3D network structure offers large open pores, high surface areas, and self‐supported properties. Third, the surfactant‐free strategy results in a relatively clean surface. These factors all contribute to better electrocatalytic activity and durability towards ethanol oxidation. Moreover, the use of copper in the alloy lowers the price of the catalyst by replacing the noble metal palladium with non‐noble metal copper. The composition‐optimized Pd₈₀Cu₂₀ alloy in the 3D NNC catalyst shows an increased electrochemically active surface area (80.95 m² g^?1) and a 3.62‐fold enhancement of mass activity (6.16 A mg^?1) over a commercial Pd/C catalyst.     

Facile Synthesis of PdCu Echinus‐Like Nanocrystals as Robust Electrocatalysts for Methanol Oxidation Reaction

Exploiting high‐performance and inexpensive electrocatalysts for methanol electro‐oxidation is conductive to promoting the commercial application of direct methanol fuel cells. Here, we present a facile synthesis of echinus‐like PdCu nanocrystals (NCs) via a one‐step and template‐free method. The echinus‐like PdCu NCs possess numerous straight and long branches which can provide abundant catalytic active sites. Owing to the novel nanoarchitecture and electronic effect of the PdCu alloy, the echinus‐like PdCu NCs display high electrocatalytic performance toward methanol oxidation reaction in an alkaline medium. The mass activity of echinus‐like PdCu NCs is 1202.1 mA mg_Pd^?1, which is 3.7 times that of Pd/C catalysts. In addition, the echinus‐like structure, as a kind of three‐dimensional self‐supported nanoarchitecture, endows PdCu NCs with significantly enhanced stability and durability. Hence, the echinus‐like PdCu NCs hold prospect of being employed as electrocatalysts for direct alcohol fuel cells.     

Rapid Aqueous Synthesis of Large-Size and Edge/Defect-Rich Porous Pd and Pd-Alloyed Nanomesh for Electrocatalytic Ethanol Oxidation

In this work, a facile aqueous synthesis strategy was used (complete in 5 min at room temperature) to produce large-size Pd, PdCu, and PdPtCu nanomeshes without additional organic ligands or solvent and the volume restriction of reaction solution. The obtained metallic nanomeshes possess graphene-like morphology and a large size of dozens of microns. Abundant edges (coordinatively unsaturated sites, steps, and corners), defects (twins), and mesopores are seen in the metallic ultrathin structures. The formation mechanism for porous Pd nanomeshes disclosed that they undergo oriented attachment growth along the ⟨111⟩ direction. Owing to structural and compositional advantages, PdCu porous nanomeshes with certain elemental ratios (e. g., Pd₈₇Cu₁₃) presented enhanced electrocatalytic performance (larger mass activity, better CO tolerance and stability) toward ethanol oxidation.     

Single-Atom or Dual-Atom in TiO2 Nanosheet: Which is the Better Choice for Electrocatalytic Urea Synthesis?

As rising star materials, single-atom and dual-atom catalysts have been widely reported in the electro-catalysis area. To answer the key question: single-atom and dual-atom catalysts, which is better for electrocatalytic urea synthesis? we design two types of catalysts via a vacancy-anchorage strategy: single-atom Pd₁−TiO₂ and dual-atom Pd₁Cu₁−TiO₂ nanosheets. An ultrahigh urea activity of 166.67 mol_urea mol_Pd⁻¹ h¹ with the corresponding 22.54 % Faradaic efficiency at −0.5 V vs. reversible hydrogen electrode (RHE) is achieved over Pd₁Cu₁−TiO₂, which is much higher than that of Pd₁−TiO₂. Various characterization including an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and theoretical calculations demonstrate that dual-atom Pd₁Cu₁ site in Pd₁Cu₁−TiO₂ is more favorable for producing urea, which experiences a C−N coupling pathway with a lower energy barrier compared with Pd₁ in Pd₁−TiO₂.     

Supported Pd–Cu Bimetallic Nanoparticles That Have High Activity for the Electrochemical Oxidation of Methanol

Monodisperse bimetallic Pd–Cu nanoparticles with controllable size and composition were synthesized by a one‐step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd₈₅–Cu₁₅, Pd₅₆–Cu₄₄, and Pd₃₉–Cu₆₁. The nanoparticles were separated from the solution mixture by extraction with non‐polar solvents, such as n‐hexane. Monodisperse bimetallic Pd–Cu nanoparticles with narrow size‐distribution were obtained without the need for a size‐selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as‐prepared nanoparticles were loaded onto a Vulcan XC‐72 carbon support. Supported bimetallic Pd–Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd–Cu catalyst that contained 15 % Cu, the activity was even comparable to the state‐of‐the‐art commercially available Pt/C catalysts. A STEM‐HAADF study indicated that the formation of random solid‐solution alloy structures in the bimetallic Pd₈₅–Cu₁₅/C catalysts played a key role in improving the electrochemical activity.     

Surface composition of PdCuAu ternary alloys: a combined LEIS and XPS study

PdCuAu ternary alloy samples with different composition were synthesized on top of ZrO₂‐modified porous stainless steel disks by the sequential electroless deposition technique. The structure, morphology and bulk composition of the samples were characterized by X‐ray diffraction (XRD), scanning electron microscopy and energy dispersive X‐ray spectroscopy (EDX). Complete alloy formation with a pure fcc phase for the Pd₇₁Cu₂₆Au₃, Pd₇₀Cu₂₅Au₅ and Pd₆₇Cu₂₄Au₉ samples and a bcc structure for the Pd₆₂Cu₃₆Au₂ and Pd₆₀Cu₃₇Au₃ samples were obtained upon annealing at 500 °C for 120 h as revealed by XRD. A combination of low‐energy ion scattering (LEIS) and X‐ray photoelectron spectroscopy (XPS) was used to investigate the surface properties of the PdCuAu alloys. XPS results confirmed alloy formation under the annealing conditions. XPS analysis also revealed that the near‐surface regions of the alloys became enriched in Pd with respect to the bulk composition determined by EDX. In contrast, LEIS and angle‐resolved XPS analyses showed that the top‐most surface layers in all samples were copper‐rich compared with the bulk composition. This high Cu surface concentration could impart resistance to bulk sulfide formation to the PdCuAu alloy membranes. Copyright © 2015 John Wiley & Sons, Ltd.     

Catalytic dehydrogenation of natural terpenes via CuPd alloy nanoparticles generated on mesoporous graphitic carbon nitride

A facile wet-chemical protocol for the synthesis of bimetallic CuPd alloy nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (m-gCN), serving as both stabilizer and support material, was presented herein. The presented protocol allowed to synthesize nearly monodisperse CuPd alloy NPs with an average particle size of 3.9 ± 0.9 nm without use of any additional surfactants and to prepare CuPd/m-gCN nanocatalysts with different Cu/Pd compositions (Cu₂₅Pd₇₅/m-gCN, Cu₃₅Pd₆₅/m-gCN, Cu₁₆Pd₇₄/m-gCN, Cu₃₂Pd₆₈/m-gCN, Cu₁₀Pd₉₀/m-gCN, and Cu₅₀Pd₅₀/m-gCN). After the detailed characterization of CuPd/m-gCN nanocatalysts, they were utilized as catalysts in the dehydrogenation of terpenes. Among all tested nanocatalysts, Cu₅₀Pd₅₀/m-gCN showed the highest activity in terms of the product yields within the same reaction time. Various parameters influencing the catalytic activity of Cu₅₀Pd₅₀/m-gCN were studied using himachalene as a model substrate and the optimum conditions were determined. Under the optimized reaction conditions, the catalytic application of Cu₅₀Pd₅₀/m-gCN nanocatalysts was extended to nine different terpenes and the corresponding products were obtained in high conversion yields (>90%) under mild conditions. A reusability test showed that Cu₅₀Pd₅₀/m-gCN nanocatalysts can be re-used up to four cycles without significant loss in their initial activity.     

Programmable Self‐Assembly of Heterometallic Palladium(II)–Copper(II) 1D Grid‐Chain using Dinuclear Palladium(II) Corners with Pyrazole–Carboxylic Acid Ligands

A novel heterometallic diPd^II–diCu^II grid‐chain, {[(bpy)₄Pd₄Cu₂L₄](NO₃)₄}_n ( 2 ; bpy=2,2′‐bipyridine), was synthesized through a programmable self‐assembly approach from the molecular corners [(bpy)₂Pd₂(HL)(L)](NO₃) ( 1 ) as linkers with Cu^II nitrate by using the bifunctional H₂L ligand featuring primary (pyrazole) and secondary (benzoic acid) groups. Structural analysis revealed that 1D structure 2 consists of one [Cu₂(O₂CPh)₄]_n unit as a bridge and two [(bpy)₂Pd₂L₂]_n corners. Additionally, the catalytic effect of the heterometallic synergy on the Suzuki coupling reaction by using 2 was further explored.     

Real-time monitoring of metal deposition and segregation phenomena during preparation of PdCu membranes

The N₂ and H₂ evolution, respectively, were monitored during deposition of Pd and Cu from electroless plating baths to obtain in-process control of the composition during preparation of 3–7 μm thick PdCu membranes on tubular ceramic substrates. Compositions estimated by gas evolution compare favorably to those measured in post-mortem XRD and EDS analyses, mostly differing by not more than 1 at.%. This result suggests that use of gas evolution measurements to enable in-process control of composition to within 1 at.% is feasible. Annealing experiments in an H₂ atmosphere demonstrated that, at 893 K, only 48 h are needed to form a stoichiometrically homogeneous, 9.5 μm thick, face centered cubic (fcc) Pd₆₃Cu₃₇ membrane from sequentially deposited layers; at 723 K, the same transformation requires over 2 weeks. The appearance of transient body centered cubic (bcc) and fcc phases with lower Pd contents signaled compositional segregation in the initial stages of alloy formation at 723 and 773 K and could be a source of persistent stoichiometric heterogeneity particularly in bcc PdCu membranes. The H₂ fluxes of fcc Pd₅₈Cu₄₂ and Pd₇₀Cu₃₀ membranes were J_H2=(1.6±1.1) mol m⁻² s⁻¹ exp[(−24.8±0.4)kJ mol⁻¹/RT] and J_H2=(3.7±0.6) mol m⁻² s⁻¹ exp[(−21.3±1.0)kJ mol⁻¹/RT], respectively, at 100 kPa H₂ pressure difference.     

Palladium Catalysis for Aerobic Oxidation Systems Using Robust Metal–Organic Framework

Described here is a new and viable approach to achieve Pd catalysis for aerobic oxidation systems (AOSs) by circumventing problems associated with both the oxidation and the catalysis through an all‐in‐one strategy, employing a robust metal–organic framework (MOF). The rational assembly of a Pd^II catalyst, phenanthroline ligand, and Cu^II species (electron‐transfer mediator) into a MOF facilitates the fast regeneration of the Pd^II active species, through an enhanced electron transfer from in situ generated Pd⁰ to Cu^II, and then Cu^I to O₂, trapped in the framework, thus leading to a 10 times higher turnover number than that of the homogeneous counterpart for Pd‐catalyzed desulfitative oxidative coupling reactions. Moreover, the MOF catalyst can be reused five times without losing activity. This work provides the first exploration of using a MOF as a promising platform for the development of Pd catalysis for AOSs with high efficiency, low catalyst loading, and reusability.     

Synthesis,Structures and Spectroscopic Properties of Platinum(II), Palladium(II) and Copper(I) Halide Complexes with Pyrimidine‐phosphine Ligand

The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of Pt^II, Pd^II and Cu^I provide three new halide metal complexes, Pt₂Cl₄(μ‐L)₂·2CH₂Cl₂ ( 1 ), Pd₂Cl₄(μ‐L)₂ ( 2 ), and [Cu₂(μ‐I)₂L₂]_n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively.     

Calorimetric investigation of order–disorder transition in Cu0.6Pd0.4 and Cu0.85Pd0.15 alloys

Order–disorder phase transitions in Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys have been investigated using differential scanning calorimetry and drop calorimetry. The differential scanning calorimetry measurements show that the transition in both these alloys are reversible in nature and the enthalpy increment measurements reveal that these transitions are first order in nature. The transition temperature of first-order phase transition in Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys have been evaluated to be 884(±2) and 799(±2) K, respectively, from drop calorimetric measurements. The latent heat of first-order phase transition in Cu_0.6Pd_0.4 alloy were evaluated to be 31.2(±0.6) and 28.9(±0.5) J g^?1, by enthalpy increment and differential scanning calorimetry measurements, respectively. Similarly, the latent heat of first-order phase transition in Cu_0.85Pd_0.15 alloy were evaluated to be 23.1(±0.6) and 21.3(±0.5) J g^?1, by enthalpy increment and differential scanning calorimetry measurements, respectively. The solidus temperatures of Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys were found to be 1,457(±2) and 1,360 K, respectively.     

Crystal‐Phase‐Engineered PdCu Electrocatalyst for Enhanced Ammonia Synthesis

Crystal phase engineering is a powerful strategy for regulating the performance of electrocatalysts towards many electrocatalytic reactions, while its impact on the nitrogen electroreduction has been largely unexplored. Herein, we demonstrate that structurally ordered body‐centered cubic (BCC) PdCu nanoparticles can be adopted as active, selective, and stable electrocatalysts for ammonia synthesis. Specifically, the BCC PdCu exhibits excellent activity with a high NH₃ yield of 35.7 μg h^?1 mg^?1_cat, Faradaic efficiency of 11.5 %, and high selectivity (no N₂H₄ is detected) at ?0.1 V versus reversible hydrogen electrode, outperforming its counterpart, face‐centered cubic (FCC) PdCu, and most reported nitrogen reduction reaction (NRR) electrocatalysts. It also exhibits durable stability for consecutive electrolysis for five cycles. Density functional theory calculation reveals that strong orbital interactions between Pd and neighboring Cu sites in BCC PdCu obtained by structure engineering induces an evident correlation effect for boosting up the Pd 4d electronic activities for efficient NRR catalysis. Our findings open up a new avenue for designing active and stable electrocatalysts towards NRR.     

Synthese,Strukturen und X‐/Q‐Band‐EPR‐Untersuchungen von N,N‐Diethyl‐N′‐3,5‐di(trifluormethyl)benzoylthioureato‐Komplexen des CuII,NiII und PdII sowie EPR‐spektroskopische Charakterisierung eines CuII‐CuII‐Dimers

The synthesis and the structures of (i) the ligand N,N‐Diethyl‐N′‐3,5‐di(trifluoromethyl)benzoylthiourea HEt₂dtfmbtu and (ii) the Ni^II and Pd^II complexes of HEt₂dtfmbtu are reported. The ligand coordinates bidendate forming bis chelates. The Ni^II and the Pd^II complexes are isostructural. The also prepared Cu^II complex could not be characterized by X‐ray analysis. However, the preparation of diamagnetically diluted powders Cu/Ni(Et₂dtfmbtu)₂ and Cu/Pd(Et₂dtfmbtu)₂ suitable for EPR studies was successful. The EPR spectra of the Cu/Ni and Cu/Pd systems show noticeable differences for the symmetry of the CuS₂O₂ unit in both complexes: the Cu/Pd system is characterized by axially‐symmetric g< and A ^cu tensors; for the Cu/Ni system g and A ^Cu have rhombic symmetry. EPR studies on frozen solutions of the Cu^II complex show the presence of a Cu^II‐Cu^II dimer which is the first observed for Cu^II acylthioureato complexes up to now. The parameters of the fine structure tensor were used for the estimation of the Cu^II‐Cu^II distance.     

Influence of Pd deposition pH value on the performance of Pd-CuO/SiO2 catalyst for semi-hydrogenation of 2-methyl-3-butyn-2-ol（MBY）

The selective hydrogenation of C≡C to C=C bonds is an important step, yet remains to be a great challenge in chemical industry. In this study, we have revealed the influence of Pd deposition pH value on the catalytic performance of Pd-CuO/SiO₂ catalyst for the semi-hydrogenation of 2-methyl-3-butyn-2-ol（MBY）. Trace amount of Pd（about 500 ppm） was loaded via deposition-reduction method on CuO/SiO₂ support by using H₂PdCl₄ solution as precursor and NaBH<...     

Modification of palladium–copper thin film by reduced graphene oxide or platinum as catalyst for Suzuki–Miyaura reactions

This study describes the synthesis of PdCu, PdCu/reduced graphene oxide and PtPdCu nanoparticle thin films via a simple reduction of organometallic precursors including [PtCl₂(cod)] and [PdCl₂(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene) complexes, in the presence of [Cu(acac)₂] (acac = acetylacetonate) complex at toluene–water interface. The structure and morphology of the thin films were characterized using energy‐dispersive analysis of X‐rays, X‐ray diffraction and transmission electron microscopy techniques. Our studies show that all of these nanoparticles are suitable for the Suzuki–Miyaura coupling (SMC) reaction in water. PtPdCu and PdCu thin films showed higher catalytic activity compared to Pd thin film in the SMC reaction due to the appropriate interaction among palladium, platinum and copper metals.     

Metallkomplexe naphthyl‐substituierter Thioharnstoffderivate

Metal Complexes of Naphthyl‐substituted Thiourea Derivatives The thiourea derivative N, N‐diethyl‐N′‐2‐naphthoylthiourea ( 1 ) and three N‐(dialkylaminothiocarbonyl)‐N′‐(1‐naphthyl)‐arylamidines ( 2 ‐ 4 ) have been synthesized and Cu^II‐, Ni^II‐ and Pd^II‐complexes of them have been prepared. According to the X‐ray structure analyses 1 with Cu^II and Ni^II under deprotonation forms neutral bis‐chelates of nearly square‐planar coordination with a cis arrangement of the O and S ligator atoms. Using their N and S atoms in 1, 3 position as ligators, 2 ‐ 4 in deprotonated form coordinate to Cu^II and Pd^II as neutral bis‐chelates, in the case of Cu^II with a distorted tetrahedral coordination. Pd^II is coordinated square planar and has, probably due to the spatial influence of the 1‐naphthyl groups, a trans arrangement of the N and S ligator atoms.     

The Role of Pd2+/Pd0 in Hydrogenation by [Pd(2‐pymo)2]n: An X‐ray Absorption and IR Spectroscopic Study

The metal–organic framework (MOF) [Pd(2‐pymo)₂]_n (2‐pymo=2‐pyrimidinolate) was used as catalyst in the hydrogenation of 1‐octene. During catalytic hydrogenation, the changes at the metal nodes and linkers of the MOF were investigated by in situ X‐ray absorption spectroscopy (XAS) and IR spectroscopy. With the help of extended X‐ray absorption fine structure and X‐ray absorption near edge structure data, Quick‐XAS, and IR spectroscopy, detailed insights into the catalytic relevance of Pd²⁺/Pd⁰ in the hydrogenation of 1‐octene could be achieved. Shortly after exposure of the catalyst to H₂ and simultaneously with the hydrogenation of 1‐octene, the aromatic rings of the linker molecules are hydrogenated rapidly. Up to this point, the MOF structure remained intact. After completion of linker hydrogenation, the linkers were also protonated. When half of the linker molecules were protonated, the onset of reduction of the Pd²⁺ centers to Pd⁰ was observed and the hydrogenation activity decreased, followed by fast reduction of the palladium centers and collapse of the MOF structure. Major fractions of Pd⁰ are only observed when the hydrogenation of 1‐octene is almost finished. Consequently, the Pd²⁺ nodes of the MOF [Pd(2‐pymo)₂]_n are identified as active centers in the hydrogenation of 1‐octene.     

Palladium‐Catalyzed Alkoxycarbonylation of Terminal Alkenes To Produce α,β‐Unsaturated Esters: The Key Role of Acetonitrile as a Ligand

A mild protocol has been developed for the Pd^II‐catalyzed alkoxycarbonylation of terminal olefins to produce α,β‐unsaturated esters with a wide range of substrates. Key features are the use of MeCN as solvent (and/or ligand) to control the reactivity of the intermediate Pd complexes and the combination of CO with O₂, which facilitates the Cu^II‐mediated reoxidation of the Pd⁰ complex to Pd^II and prevents double carbonylation.     

Chelatbildung mit 1,3-Diamino-2-methylenpropanen

Chelate Formation with 1,3-Diamino-2-methylene Propane1 1,3-Diamino-2-methylene propane and its N, N′ alkylated derivatives form crystalline chelates with Co^II (1:3), Ni^II (1:1, 1:2 and 1:3), Pd^II (1:1, 1:2), Rh^III (1:1) and Cu^II (1:2). Experiments for preparation of olefin complexes were unsuccessful. By potentiometric measurements the base strengths of the ligands as well as the stability constants of the Co^II, Ni^II, Pd^II, Cu^II, Zn^II, Cd^II chelates were evaluated and the kinetics of the formation of the 1:1 Pd^II complex is investigated. The magnetic behaviour of the Co^II?, Pd^II? and Cu^II? chelates is normal, whereas[Ni(dia)₂(H₂O)₂] (ClO₄)₂ shows anormal behaviour due to configurational isomerism between square planar and octahedral ligand geometry in solid state in type of a LIFSCHITZ -isomerism. The ESR-spectra of the Cu^II?compounds are discussed and the bonding parameters of the Cu? N?bonds were calculated.