Pd-Ni Nanoparticles Research Articles

Research of surface diffusion and growth of Ni-Pd nanoparticles

ABSTRACT Building upon the foundation of embedded atom method potential, this study employs the Nudged Elastic Band method to computationally investigate the diffusion and structural behaviour of Ni-Pd bimetallic nanoparticles on Wulff surfaces. The results reveal that, whether Ni or Pd serves as the substrate, the energy barrier is significantly lower when adatom exchange occurs with two adjacent (111) interfacet atoms compared to the interfacet of (111) and (100). The optimal diffusion path is identified as the centre-positive diagonal exchange (CPDE). Furthermore, it is observed that the energy of the system decreases after the exchange diffusion with the substrate surface atoms. However, successful exchange diffusion requires overcoming specific energy barriers (>0.43 eV), enabling the deposition of NicorePdshell and PdcoreNishell nanoparticles at low temperatures. In Ni-Pd nanoparticles, surface energy plays a predominant role when the size is very small (Natom≦55), leading to the stable configuration of NicorePdshell nanoclusters. However, as the size increases, the impact of bond energy becomes more pronounced, resulting in an alloyed structure as the stable configuration. Furthermore, in cases where the proportion of Pd atoms is small, all Pd atoms are situated on the surface, displaying a discrete distribution morphology.

MgAl hydrotalcite supported ultrafine PdNi bimetallic catalyst for the dehydrogenation of dodecahydro-N-ethylcarbazole

Liquid organic hydrogen storage is a promising way of storing hydrogen. The development of efficient and low-cost dehydrogenation catalysts is still required to advance the commercialization of N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NEC/H12-NEC) hydrogen storage and transport system.In this paper, PdNi bimetallic catalyst (Pd3Ni1/LDHs) supported on MgAl hydrotalcite was prepared by NaBH4 and ultrasound-assisted stepwise reduction. Ultrasonic cavitation could excite the hydroxyl hydrogen of hydrotalcite in the form of hydrogen radicals to reduce PdCl42− to Pd nanoparticles (NPs), and also promoted the formation of PdNi alloys as well as the dispersion of NPs. In the Pd3Ni1/LDHs catalyst, the average particle size of NPs was 1.98 nm, suggesting an excellent dispersion of Pd, Ni, and PdNi NPs. The electronic effects of Ni and Pd significantly improved the catalytic efficiency of Pd3Ni1/LDHs in H12-NEC dehydrogenation, resulting in a hydrogen release rate of 98.4 % after 6 h at 180 °C, surpassing that of Pd/LDHs. It can be considered that the dehydrogenation performance of Pd3Ni1/LDHs for H12-NEC is related to the alloy phase, electronic structure and NPs size.

Preparing uniform supported Pd-Ni catalysts with citrate-assisted impregnation

Bimetallic supported catalysts can show synergistic effects compared to their monometallic constituents. However, it is challenging to produce bimetallic catalysts with a uniform nanoparticle distribution over the support, while ensuring each nanoparticle contains both metals. A promising strategy is to use impregnation precursors that facilitate uniform distribution of both metals over a support. In this work, citrate-based precursors were studied to prepare bimetallic Pd-Ni nanoparticles supported on SBA-15 mesoporous silica. Amongst others, cryo-electron microscopy demonstrated the excellent distribution of Ni citrate precursor after drying. Co-impregnation with Ni citrate precursor and Pd(OAc)2 or Pd(NH3)4(NO3)2 produced well-distributed Pd-Ni nanoparticles with a narrow particle size distribution. Extensive characterization with STEM-EDX, EXAFS and TPR showed that the type of Pd precursor controlled the Pd to Ni nanoscale intimacy. CO2 hydrogenation experiments demonstrated that increasing Pd-Ni intimacy decreased the activity. Our strategy to produce uniform Pd-Ni nanoparticles using citric acid is relevant also for other bimetallic systems.

Redox transmetallation reaction mediated synthesis of Ni-Pd bimetallic nanocatalyst for pesticide degradation to value added product

In this work a wet-chemical recipe has been accounted for the synthesis of bimetallic Ni-Pd nanostructures at ambient condition involving pre-synthesized nickel nanoparticles and aqueous tetrachloropalladate, [PdCl4]2- solution. The Galvanic replacement reaction (GRR) starts instantaneously between less noble Ni0 nanoparticle i.e., zero valent nickel (ZVN) and more noble [PdCl4]2-. Thus ZVN is oxidatively etched out as soluble Ni2+ by more noble [PdCl4]2- depositing Pd0 onto the residual ZVN. Concurrently the Ni2+ ions move outwardly into the bulk solution and the Pd0enters into the inwardly fashion owing to their different diffusivities and results in the formation of hollow bimetallic nanostructures following diffusion limited nanoscale Kirkendall effect. Finally, the bimetallic nanomaterial was shown to be a competent heterogeneous catalyst for facile hydrolytic degradation of an organothiophosphate pesticide, methyl parathion (MP). After the completion of the degradation, the degraded product, 4-nitrophenolate (4-NP) was subsequently reduced to 4-aminophenolate (4-AP) in the same reaction pot in presence of the same catalyst using borohydride. 4-AP is the principal ingredient for the production of the medicine paracetamol. Hence the bimetallic Ni-Pd nanoparticles turn out to be a promising heterogeneous catalyst for water pollution abatement through pesticide degradation vis-à-vis generation of value added product out of the degraded product of the pesticide.

Bimetallic PdCo and PdNi Nanoparticles Supported on Covalent Organic Frameworks as Catalysts for the Hydrogenation of 4-Nitrophenol

Bimetallic PdCo and PdNi Nanoparticles Supported on Covalent Organic Frameworks as Catalysts for the Hydrogenation of 4-Nitrophenol

The Positive Effects of Carbon-Coating Layers on Protecting the Nanoparticle Towards Poisoning Ions or Gases

Recently, the research that explores the positive effects of carbon-coating nanoparticles to fight the severe oxidation/corrosion in Alkaline fuel cell (AFC), Proton-exchange membrane fuel cell (PEMFC) or water electrolyzer is well-recognized, since the carbon layers can extend the catalyst’s durability towards hydrogen oxidation/evolution reactions (HOR, HER) and oxygen evolution/reduction reactions (OER, ORR). Especially for the reactions in alkaline pH, with the graphite coating, the Ni nanoparticles in both HOR and HER can resist passivation and hydride poisoning. [1,2] Similarly, in the same alkaline conditions, the amorphous carbon coating slows down the degradation of Pd catalysts.[3] Moreover, the coating can block big ions such as halide, thus benefiting Pt group metals from resisting halide adsorption, that eventually prevents the dissolution of metal.[4,5]In this work, we examined the gas poisoning effects on coated catalysts. For example, we synthesized carbon-coated Pd-Ni nanoparticles, supported on Vulcan carbon and studied its electrochemical response in 0.1M KOH at room temperature and its tolerance towards CO gas. As a result, Pd-Ni coated had better resistance to passivation compared to the non-coated Pd-Ni catalyst. It also showed that the thickness of the carbon coating layers was sufficient to block the CO absorption in RDE condition initially (Figure 1, black solid line). Only after 150 cycles of accelerated stress test in Ar (AST-Ar, using potential stepping between 0.1 and 1.23 V vs. RHE with a pulse of 3 s at each potential in Ar-saturated electrolyte, 6s/cycles), the passivation that occurred at high potential could cause a small portion of Pd to be “exposed” and adsorb CO (Figure 1, red solid line). After another 150 cycles of AST-Ar (AST 300), more Pd was exposed to CO adsorption but not fully. This proves the carbon-coating layers can protect the nanoparticles from poison contaminant gas such as NOx, SOx, CO, or the COx-like species. Both AFC and PEMFC systems can benefit from this type of catalyst to operate extensively without losing catalytic activity to passivation or pollution issues.

Hexagonal boron nitride sheet-anchored palladium‑nickel nanoparticles for highly selective hydrogenation of cinnamaldehyde under mild conditions

Selective hydrogenation of cinnamaldehyde toward hydrocinnamaldehyde is an extremely important and challenging reaction. Herein, ultrafine PdNi bimetallic nanoparticles with different Pd to Ni ratios were uniformly anchored on hexagonal boron nitride nanosheet (BNNS) by a coprecipitation-reduction method. The resulting Pd4Ni0.6/BNNS (4 wt% Pd and 0.6 wt% Ni with respect to BNNS) catalyst displayed the excellent catalytic performance and gave the hydrocinnamaldehyde selectivity of 94 % with quantitative conversion of cinnamaldehyde under atmospheric pressure at 60 °C. Moreover, Pd4Ni0.6/BNNS had excellent reusability with a conversion of 92 % and a hydrocinnamaldehyde selectivity of 85 % after three recycle process. The high catalytic performance of BNNS-anchored PdNi nanoparticles was likely due to the synergy of PdNi and the alteration of electronic and surface properties of Pd by reasonable interactions between bimetallic nanoparticles and BNNS support.

High durability for PdNi nano-film hydrogen sensor

Stability is a critical parameter for hydrogen (H2) sensors. To enhance stability, we investigated the microstructure and morphology of palladium-nickel (PdNi) nano-film H2 sensors under various sputter pressures and annealing temperatures. Our findings indicate that an increase in the work sputtering pressure reduces the energy of the sputtering atom, resulting in the formation of small gaps between the PdNi nanoparticles at a pressure of 5 Pa. Furthermore, compared to the (111) peak position of pure Pd, the lattice constant of the prepared PdNi nano-film is significantly reduced. At 300 °C, the surface grains exhibit tip passivation. We conducted 20 cyclic tests for 1% H2 concentration of PdNi nano-film sensors, and our repeatability tests demonstrate that small cracks between two PdNi nanoparticles effectively alleviate particle expansion caused by H absorption. However, during the cycles of 1% H2 or N2, significant fluctuations were observed in the response resistance (Rs) and recovery resistance (Ra) during the stable phase. As the annealing temperature increases, Ra and Rs fluctuations decrease noticeably. Furthermore, the PdNi nano-film H2 sensor annealed at 300 °C exhibits high stability, relatively high Rs, short response time (trs), and short recovery time (trc).

Facile Synthesis of Multifunctional Ni(OH)2-supported Core-shell Ni@Pd Nanocomposites for the Electro-oxidation of Small Organic Molecules.

In the domain of proton exchange membrane fuel cells (PEMFCs), the development of efficient and durable catalysts for the electro-oxidation of small organic molecules, especially of alcohols (methanol, ethanol, ethylene glycol, et al.) has always been a hot topic. A large number of related electrocatalysts with splendid performance have been designed and synthesized till now, while the preparation processes of most of them are demanding on experimental operations and conditions. Herein, we put forward a facile and handy method for the preparation of multifunctional Ni(OH)2-supported core-shell Ni@Pd nanocomposites (Ni(OH)2/Ni@Pd NCs) with the assistance of galvanic replacement reaction (GRR) at room temperature and ambient pressure. As expected, the Ni(OH)2 substrate can prevent the aggregation of core-shell (CS) Ni@Pd nanoparticles (NPs) and inhibit the formation of COads and further prevent Pd from being poisoned. The synergistic effect between CS Ni@Pd NPs and Ni(OH)2 substrate and the electronic effect between Pd shell and Ni core contribute to the outstanding electrocatalytic performance for methanol, ethanol, and ethylene glycol oxidation in alkaline condition. This study provides a succinct method for the design and preparation of efficient Pd-based electrocatalysts for alcohol electro-oxidation.

Waste plastics derived nickel-palladium alloy filled carbon nanotubes for hydrogen evolution reaction

Carbon nanotubes (CNTs) composed of bimetallic nickel-palladium (NiPd) nanoparticles encapsulated in graphitic carbon shells (NdPd@CNT) are prepared by the chemical vapour deposition method using waste polyethylene terephthalate (PET) plastic carbon sources and NiPd-decorated carbon sheets (NiPd@C) catalyst. The characterization results reveal that the face-centered cubic crystalline (fcc)-structured NiPd bimetallic alloy nanoparticles are encased by thin carbon nanotubes. The bimetallic synergism of NiPd nanoparticles actuates the outer CNT layers and accelerates the electrical conductivity, stimulating the electrochemical activity toward an effective hydrogen evolution reaction (HER). By virtue of the collective individualities of highly conductive aligned carbon walls and bimetallic active sites, the NiPd@CNT-equipped HER delivers a minimum overpotential of 87 mV and a Tafel slope value of 95 mV dec−1. The existing intact contact between NiPd and CNT facilitates continuous electron and ion transportation and firm stability toward long-term hydrogen production in HER. Notably, the NiPd@CNT reported here produces excellent electrochemical activity with minimal charge transference resistance, substantiating the efficacy of NiPd@CNT for futuristic green hydrogen production.

Highly Dispersed PdNi Nanoparticles on an Oxygen-Functionalized Activated Carbon with Extraordinary Electrocatalytic Activity for Methanol Oxidation

Highly Dispersed PdNi Nanoparticles on an Oxygen-Functionalized Activated Carbon with Extraordinary Electrocatalytic Activity for Methanol Oxidation

N-doped carbon-stabilized PdNiCu nanoparticles derived from PdNi@Cu-ZIF-8 as highly active and durable electrocatalyst for boosting ethanol oxidation

Controlling the component, tailoring the size and designing the carbon supporting materials are three promising strategies to improve electrocatalytic activity. Herein, a monatomic Cu carrier (CuCN) with larger specific surface area was used to anchor PdNi alloy nanoparticles by a facile one-step reduction method. Physical characterization revealed that the PdNi nanoparticles in the synthesized material possess good dispersion, which is mainly attributed to the high specific surface area of CuCN-900.Electrochemicalresults revealed that CuCN supported PdNi nanoparticles (Pd1Ni1/CuCN-900) nanohybrids had superior durability and catalytic activity for ethanoloxidation (EOR) compared with that of other PdxNiy/CuCN and commercial Pd/C. Rotating disk electrode (RDE) results further demonstrated that Pd1Ni1/CuCN-900 has a faster kinetic process of EOR than commercial Pd/C. DFT calculation implies that OH adsorption is preferentially near the Ni atom, the OH species on Ni1Pd1 surface play an important role in the process of EOR. This is of great research implications for finding new carbon carriers and regulating catalyst components to improve the catalytic efficiency of PdNi catalysts.

Valuation of bimetallic Pd/Ni nanoparticles catalyst for the applications in direct methanol fuel cells

AbstractThe electrospinning method has been successfully employed to prepare various percentages of less expensive nickel/palladium (NP) nanofiber catalysts as an alternative to platinum in direct methanol fuel cells (DMFC). The chemical structure, morphological characteristics, and electrochemical (EC) properties have been investigated using a variety of analysis techniques. According to the scanning electron microscope (SEM), all prepared samples with different Pd concentrations exhibit good nanofiber form and a distinct nanoparticle look. Transmission electron microscopy (TEM) reveals an amorphous carbon nanofiber structure with imbedded crystalline spheres of nickel and palladium. The carbonized polyvinyl alcohol nanofibers (PVANFs) have a steady and even distribution of nickel and palladium with an accurate nickel and palladium content, according to the energy dispersive X‐ray mapping results. The lack of hydroxide or oxide phases in the X‐ray diffraction (XRD) pattern proves that Ni–Pd nanoparticles are present in the metallic phase. For the electrooxidation of methanol, urea, and an isopropanol‐methanol mixture, the electrocatalytic features of the fabricated samples have been examined. EC results show that methanol has the best electrocatalytic properties. Hence, NP nanofiber catalysts could be a promising candidate to replace platinum in DMFC.

Synthesis, characterization, and enhanced hydrogen generation from NaBH4 methanolysis of highly dispersed bimetallic PdNi nanoparticles supported on Vulcan carbon

In this presented work, the bimetallic palladium-nickel nanoparticles (PdNi NPs) supported by Vulcan carbon (VC) were synthesized by chemical method. The morphological structure of the synthesized PdNi@VC NPs was determined by ultraviolet-visible spectrum (UV–Vis), Fourier infrared spectrometry (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD) characterization performed. According to the characterization results obtained, the size of the NPs was found to be 8.523 ± 2.036 nm. Then, hydrogen production efficiencies were tested according to different temperatures, substrate, and catalyst concentrations. Finally, the reusability test was performed. According to the results obtained, the hydrogen average production efficiency of NPs was calculated as 84%. The activation energy (Ea), enthalpy (ΔH), and entropy (ΔS) values of the catalyst were found to be 54.2 kJ/mol, 51.7 kJ/mol, -134.5 J/mol.K, respectively. This study guides the new catalytic energy production studies to be carried out on nanotechnological platforms. These synthesized nanoparticles can be developed to be an efficient catalyst for hydrogen generation as an alternative energy source.

Component dependent electrocatalytic activity of magnetic bimetallic Pd-Ni nanoparticles for formate oxidation

Formate fuel cells require efficient and stable electrocatalysts for formate oxidation reaction (FOR). Pd-Ni nanoparticles (NPs) with tuned Pd/Ni ratios were synthesized by seed-mediated growth strategy. Pd-Ni NP-3 NPs outperformed other Pd-based catalysts in FOR activity (∼28676 mA/mgPd). This enhancement resulted from the component-dependent effects, which modulate the Pd(0) and Ni(OH)2 species, and resulting in an optimal balance of effective active sites and anti-poisoning ability.

Combined Steam and CO2 Reforming of Methane over Ni-Based CeO2-MgO Catalysts: Impacts of Preparation Mode and Pd Addition

The sol–gel template technique makes it possible to synthesize a stable and efficient nickel catalyst based on magnesium-modified cerium oxide Ce0.5Mg0.5O1.5 for the combined steam and CO2 reforming of methane. To stabilize dispersed forms of the active component in the matrix of the support, the catalysts were synthesized by changing the support precursor (cerium acetate and chloride), the active component composition (Ni, NiPd) and the method of introducing nanoparticles. The relationship was established between the physicochemical and catalytic characteristics of the samples. The use of cerium acetate as a support precursor provided smaller pore and crystallite sizes of the support, a stabilization of the dispersed forms of the active component, and excellent catalytic characteristics. The introduction of Pd into the Ni nanoparticles (Pd/Ni = 0.03) increased the resistance of the active component to sintering during the reaction, ensuring stable operation for 25 h of operation. The increased stability was due to a higher concentration of defective oxygen, a higher dispersion of bimetallic NiPd nanoparticles, and the Ni clusters strongly interacting with the NiO-MgO solid solution. An efficient and stable Ni0.194Pd0.006Ce0.4Mg0.4O1.4 catalyst for the conversion of CO2 into important chemicals was developed. With the optimal composition and synthesis conditions of the catalyst, the yield of the target products was more than 75%.

Electrospun NiPd Nanoparticles Supported on Polymer Membrane Nanofibers as an Efficient Catalyst for NaBH4 Dehydrogenation.

Sodium borohydride (SBH) hydrolysis in the presence of cheap and efficient catalysts has been proposed as a safe and efficient method for generating clean hydrogen energy for use in portable applications. In this work, we synthesized bimetallic NiPd nanoparticles (NPs) supported on poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers (PVDF-HFP NFs) via the electrospinning approach and reported an in-situ reduction procedure of the NPs being prepared by alloying Ni and Pd with varying Pd percentages. The physicochemical characterization provided evidence for the development of a NiPd@PVDF-HFP NFs membrane. The bimetallic hybrid NF membranes exhibited higher H2 production as compared to Ni@PVDF-HFP and Pd@PVDF-HFP counterparts. This may be due to the synergistic effect of binary components. The bimetallic Ni1-xPdx(x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)@PVDF-HFP nanofiber membranes exhibit composition-dependent catalysis, in which Ni75Pd25@PVDF-HFP NF membranes demonstrate the best catalytic activity. The full H2 generation volumes (118 mL) were obtained at a temperature of 298 K and times 16, 22, 34 and 42 min for 250, 200, 150, and 100 mg dosages of Ni75Pd25@PVDF-HFP, respectively, in the presence of 1 mmol SBH. Hydrolysis utilizing Ni75Pd25@PVDF-HFP was shown to be first order with respect to Ni75Pd25@PVDF-HFP amount and zero order with respect to the [NaBH4] in a kinetics study. The reaction time of H2 production was reduced as the reaction temperature increased, with 118 mL of H2 being produced in 14, 20, 32 and 42 min at 328, 318, 308 and 298 K, respectively. The values of the three thermodynamic parameters, activation energy, enthalpy, and entropy, were determined toward being 31.43 kJ mol-1, 28.82 kJ mol-1, and 0.057 kJ mol-1 K-1, respectively. It is simple to separate and reuse the synthesized membrane, which facilitates their implementation in H2 energy systems.

Influence of Temperature on the Kinetic Parameters of the Pd-Ni Electroplating Process from Ethaline

In the present work, the kinetic parameters from the electrodeposition of bimetallic Pd-Ni nanoparticles on the surface of a glassy carbon electrode (GCE) were studied. These parameters are P1 directly related to the diffusion coefficient (D), P2 related to the numerical density of active sites (N0) and the nucleation frequency (A). In addition, the type of nucleation that occurs in electrodeposition, instantaneous or progressive. The electrolytic medium used was an ethaline deep eutectic solvent (DES) for electrodeposition due to its good electrochemical properties. Cyclic voltammetry (CV) and potentiostatic current density transients (j-t) were performed at two temperatures, 25 and 70 °C. The j-t values ​​were used to generate theoretical fittings using the Scharifker and Hills, and the Díaz-Morales models for bimetallic phases.

Nickel-palladium bimetallic nanoparticles supported on multi-walled carbon nanotubes; versatile catalyst for Sonogashira cross-coupling reactions.

We have developed an efficient method to generate highly active nickel-palladium bimetallic nanoparticles supported on multi-walled carbon nanotubes (Ni-Pd/MWCNTs) by dry mixing of the nickel and palladium salts utilizing the mechanical energy of a ball-mill. These nanoparticles were successfully employed in Sonogashira cross-coupling reactions with a wide array of functionalized aryl halides and terminal alkynes under ligand and copper free conditions using a Monowave 50 heating reactor. Notably, the concentration of palladium can be lowered to a minimum amount of 0.81% and replaced by more abundant and less expensive nickel nanoparticles while effectively catalyzing the reaction. The remarkable reactivity of the Ni-Pd/MWCNTs catalyst toward Sonogashira cross-coupling reactions is attributed to the high degree of the dispersion of Ni-Pd nanoparticles with small particle size of 5-10 nm due to an efficient grinding method. The catalyst was easily removed from the reaction mixture by centrifugation and reused several times with minimal loss of catalytic activity. Furthermore, the concentration of catalyst in Sonogashira reactions can be reduced to a minimum amount of 0.01 mol% while still providing a high conversion of the Sonogashira product with a remarkable turnover number (TON) of 7200 and turnover frequency (TOF) of 21 600 h-1. The catalyst was fully characterized by a variety of spectroscopic techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

Nitrogen doped mesoporous carbon supporting Pd–Ni nanoparticle as a highly efficient catalyst for C–C coupling reactions

Nitrogen doped mesoporous carbon supporting Pd–Ni nanoparticle as a highly efficient catalyst for C–C coupling reactions