Pd-Ni Alloys Research Articles

Features of the Carbon Nanofibers Growth over Ni-Pd Catalyst Depending on the Reaction Conditions

Ni-Pd alloy was prepared by a co-precipitation technique. Catalytic decomposition of a model chlorinated hydrocarbon (1,2-dichloroethane) was performed in a quartz flow-through reactor system. Both the temperature regime and the composition of the reaction mixture were varied during the experiments. Concentration of 1,2-dichloroethane was found to affect significantly the kinetics of the process, the yield of the nanostructured carbon product and its textural and morphological characteristics. In terms of optimal temperature, the maximum carbon yield was obtained within a range of 650-670 °C.

Preparation of compact and porous Pd-Ni alloys and study of their performances for ethanol oxidation in alkali

Electrodeposition and galvanic displacement reactions are used to prepare compact and porous Pd-Ni alloys and heterogeneous bilayer structures Pd/Ni or Pd/Pd-Ni. Pd is present in the deposits either as a pure metal or in solid solutions with Ni. Electrode activity in ethanol oxidation and Pd surface area are estimated by cyclic voltammetry. Results show that, in a first approximation, the peak current of ethanol oxidation is simply proportional to the Pd area, regardless of samples morphology, structure and composition, for the entire series of samples. Deviations from the proportionality relation indicate that Pd and Pd-rich alloys are more active than Ni-rich alloys of same Pd surface.

Low Concentration Response Hydrogen Sensors Based on Wheatstone Bridge.

The PdNi film hydrogen sensors with Wheatstone bridge structure were designed and fabricated with the micro-electro-mechanical system (MEMS) technology. The integrated sensors consisted of four PdNi alloy film resistors. The internal two were shielded with silicon nitride film and used as reference resistors, while the others were used for hydrogen sensing. The PdNi alloy films and SiN films were deposited by magnetron sputtering. The morphology and microstructure of the PdNi films were characterized with X-ray diffraction (XRD). For efficient data acquisition, the output signal was converted from resistance to voltage. Hydrogen (H2) sensing properties of PdNi film hydrogen sensors with Wheatstone bridge structure were investigated under different temperatures (30 °C, 50 °C and 70 °C) and H2 concentrations (from 10 ppm to 0.4%). The hydrogen sensor demonstrated distinct response at different hydrogen concentrations and high repeatability in cycle testing under 0.4% H2 concentration. Towards 10 ppm hydrogen, the PdNi film hydrogen sensor had evident and collectable output voltage of 600 μV.

Surface composition of ion bombarded nickel based alloys

The composition of NixPdy (x, y = 1, 5) and NiMoRe alloys irradiated by 3 and 4 keV Ar+ ions along the normal to the sample surface was investigated in situ by low energy ion scattering spectroscopy (LEIS). The analysis was performed using a 5 keV Ne+ ion beam. It was found that the composition of the topmost layer of bombarded NixPdy alloys nearly corresponds to the alloy stoichiometry. In the case of irradiation of the NiMoRe alloy, a surface enrichment with the heavier components (Mo and Re) was found. The thermally activated Gibbsian segregation in NiPd and NiPd5 alloys was also studied using LEIS.

Alloyed Pd[sbnd]Ni hollow nanoparticles as cocatalyst of CdS for improved photocatalytic activity toward hydrogen production

Photocatalytic hydrogen evolution has been regarded as an efficient method for H2 production, in which the cocatalysts play a crucial role. In this work, two-dimensional (2D) snow-flake CdS was synthesized via a solvothermal method. PdNi hollow alloy with different compositions were synthesized by a galvanic replacement method, and decorated on CdS surface. The structural microscopic and spectroscopic analysis demonstrated that the formation of PdNi hollow nanoparticles (HNPs) and the decoration of PdNi HNPs on CdS (PdNi/CdS). Photocatalytic hydrogen evolution reaction was performed under visible light irradiation (λ ≥ 420 nm). Pd1Ni1/CdS exhibited higher photocatalytic H2 generation rate about 54 mmol/h/g with a quantum efficiency of 63.97% at 420 nm, which was 1.7-fold higher than that of Pd/CdS (32.4 mmol/h/g). The high photocatalytic performance for Pd1Ni1/CdS was mainly attributed to the strong interaction between Pd1Ni1 HNPs and CdS, and the formation of unique hollow structure of PdNi alloy with porous nature which provided more active sites for H2 evolution. Additionally, the synergistic effect between Pd and Ni, as well as the 2D morphology of CdS enhance the mobility of photo-generated charge carriers which minimize their recombination in turn enhance the photocurrent and photocatalytic performance of solar water splitting reaction.

A cleaner route for hydrodeoxygenation of oleic acid in hexane containing pressurized CO2 over a MCF supported Fe-Pd-Ni trimetallic catalyst

Selective production of octadecane through the hydrodeoxygenation of oleic acid in hexane containing pressurized CO2, a green reaction media, using a mesocellular foam (MCF) supported Fe-Pd-Ni/MCF catalyst was demonstrated in this study. In addition to hexane containing pressurized CO2 playing a key role in directing the hydrotreatment of oleic acid towards hydrodeoxygenation over decarboxylation/decarbonylation, the use of MCF as the support helped achieve higher selectivity for octadecane, the major hydrodeoxygenation product while at the same time completely negating heptadecane, the decarboxylation/decarbonylation product. Negligible diffusion resistance aided by the 3-dimensional cage like structure and large pore opening of MCF, plus a better dispersion of the catalyst were identified as major reasons for enhancement of octadecane yield. An octadecane yield of 93% at 4 h was achieved through an optimization of temperature to 278 °C and a H2 pressure to 40 bars, while the CO2 pressure was kept constant at 20 bars. The activation energy for the hydrodeoxygenation of stearic acid to octadecane was observed to be a 43.6% reduction over the existing literature. An increased spillover of H2 onto the surface of Fe nanoparticles, triggered by an increased sticking capability of H2 on Pd-Ni alloy patches formed on the top Fe nanoparticles, was proposed as the major reason for this acceleration. The proposed catalyst could not only avoid production of undesired decarbonized product heptadecane but also reduce energy requirement to achieve higher yield over reported data due to the lowering of temperature and time, indicating its superiority.

PdNi alloy nanoparticles assembled on cobalt ferrite-carbon black composite as a fuel cell catalyst

PdNi alloy nanoparticles (NPs) were synthesized and then readily assembled on the composite of cobalt ferrite NPs with Vulcan XC-72 carbon (CoFe2O4-VC). The electrocatalyst performance of the yielded PdNi/CoFe2O4-VC composite was tested in borohydride fuel cell reactions in alkaline media. The structure/morphology of colloidal CoFe2O4 and PdNi alloy NPs along with the yielded CoFe2O4-VC composite and PdNi/CoFe2O4-VC electrocatalyst were examined by TEM, powder XRD and ICP-MS. Both monodisperse CoFe2O4 and PdNi alloy NPs with 11 and 4 nm average size, respectively, were discernible over the VC support material by the TEM images of the electrocatalyst. The loading ratio of CoFe2O4 and PdNi alloy NPs in the composite was found to be 16.1 wt% and 2.7 wt%, respectively, as determined by ICP-MS. The performance of PdNi/CoFe2O4-VC as a novel electrocatalyst for oxygen reduction (ORR) and borohydride oxidation (BOR) reactions in alkaline media was studied by voltammetric techniques using a rotating disk electrode. ORR and BOR parameters such as number of exchanged electrons and kinetic current density were calculated. The results revealed that PdNi/CoFe2O4-VC electrocatalyst was highly efficient for both ORR and BOR with exchange of 3.2 and 6.6 electrons, respectively.

Amphiphilic cellulose supported PdNi alloy nanoparticles towards biofuel upgrade under mild conditions

Design of stable high-performance heterogeneous catalysts has become crucial for efficient catalytic conversion of renewable biomass into high value-added chemicals. In this study, amphiphilic polymer support was synthesized by grafting hydrophobic groups onto hydrophilic cellulose nanocrystals and utilized as a support for PdNi alloy nanoparticles. The as-synthesized catalysts exhibited encouragingly high performance in the hydrodeoxygenation of vanillin under mild conditions.

Stabilizing electrochemical Li–O2batteries with a metal-based cathode of PdNi on Ni nonwoven fabric

The design of a nanoporous cathode for Li-O2 batteries that can achieve high chemical stability and superior electrochemical performance remains a formidable challenge. A novel approach for the fabrication of nanoengineered PdNi alloys directly coated onto Ni nonwoven fabric (PdNi/NiNF) obtained through electrospinning has been proposed. On the basis of the contributions of the porous structure, the prepared metal-based cathodes can exhibit high chemical and mechanical stabilities, high catalytic activity, and high conductivity. In this design, the major side reactions were excluded when compared with popularly used carbon cathodes, and excellent cycling stability (266 cycles) could be achieved. The proposed cathode exhibited a high discharge capacity of 15 700 mA h g-1 at 500 mA g-1, which was 5 times higher than those reported for carbon-free cathodes.

Visible-Light-Driven Efficient Hydrogen Production from CdS NanoRods Anchored with Co-catalysts Based on Transition Metal Alloy Nanosheets of NiPd, NiZn, and NiPdZn

Investigation of new catalysts to improve artificial photosynthesis efficiencies is an absolute need concerning energy demands and environmental issues. In the present study, nanosheets of NiPd, NiZn, and NiPdZn metal alloys, synthesized at the toluene–water interface, have been employed as co-catalysts for hydrogen evolution from water in the presence of CdS nanorods (NRs) as a photosensitizer. Anchoring of alloy nanosheets with CdS NRs resulted in exceptional enhancement in hydrogen evolution activity. Interestingly earth abundant cost-effective CdS/NiZn photocatalyst showed higher hydrogen evolution reaction (HER) activity than comparatively precious photocatalyst CdS/NiPd. Trimetallic alloy nanosheets of NiPdZn further exhibited superior HER activity concerning bimetallic alloys, NiZn and NiPd. An enhancement of 21 times in the hydrogen evolution activity of CdS has been achieved by optimum loading of NiPdZn. Hydrogen yields of 21347.3 μmol h–1 g–1 (AQY = 11.35%) and 53361.3 μmol h–1 g–1 (AQY = 28%) h...

Reduced graphene oxide supported PdNi alloy nanocrystals for the oxygen reduction and methanol oxidation reactions

The research on electrocatalysts with relatively lower price than Pt and excellent electrocatalytic performance for the cathode oxygen reduction reaction (ORR) and anode methanol oxidation reaction (MOR) is vital for the development of direct methanol fuel cells (DMFCs). In this work, we develop a cyanogel-reduction method to synthesize reduced graphene oxide (rGO) supported highly dispersed PdNi alloy nanocrystals (PdNi/rGO) with high alloying degree and tunable Pd/Ni ratio. The large specific surface area and the d-band center downshift of Pd result in excellent activity of Pd4Ni1/rGO nanohybrids for the ORR. The modification of Pd electronic structure can facilitate the adsorption of CH3OH on Pd surface and the highly oxophilic property of Ni can eliminate/mitigate the COads intermediates poisoning, which make PdNi/rGO nanohybrids possess superior MOR activity. In addition, rGO improve the stability of PdNi alloy nanocrystals for the ORR and MOR. Due to high activity and stability for the ORR and MOR, PdNi/rGO nanohybrids are promising to be an available bifunctional electrocatalyst in DMFCs.

Chlorobenzene hydrodechlorination on bimetallic catalysts prepared by laser electrodispersion of NiPd alloy

Abstract NiPd bimetallic systems were for the first time synthesized by laser electrodispersion (LED) of the Ni77Pd23 alloy target followed by the deposition of produced bimetallic particles on a TEM copper grid and alumina granules. Selective area energy-dispersive analysis confirms the bimetallic nature of NiPd particles deposited on a TEM copper grid. Their mean size is 1.0 nm according to TEM. XPS data demonstrate that under deposition on alumina granules (total metal content of 0.005 wt.%), nickel in bimetallic particles nearly completely oxidizes to Ni2+ species predominantly in the form of aluminate. At the same time major part of palladium (84%) exists in Pd0 but oxidizes to Pd2+ (80%) during 6 months storage in air. Both metals are deposited on the external surface of alumina granules and localized in the same areas. In situ reduction of both metals by H2 in the catalytic cell of XPS spectrometer is hindered. Nickel is not reduced even at 450°C, confirming the formation of NiAlOx, whereas palladium is reduced at higher temperatures compared to a similar monometallic catalyst. Nevertheless, NiPd/Al2O3 catalyst is more efficient in gas-phase chlorobenzene hydrodechlorination at 150–350°C than Ni/Al2O3 and even Pd/Al2O3, and much more stable. The difference may be caused by the formation of new active sites due to the contact between Pd0 and NiAlOx-modified support, and the protective action of spinel reacting with HCl by-product.

Formation of Active Sites of Carbon Nanofibers Growth in Self-Organizing Ni–Pd Catalyst during Hydrogen-Assisted Decomposition of 1,2-Dichloroethane

The Ni–Pd alloys synthesized by the coprecipitation method were studied as precursors for the self-organizing particles catalyzing the growth of carbon nanofibers. The addition of palladium was found to enhance both the activity, stability, and productivity of the catalyst in the hydrogen-assisted decomposition of 1,2-dichloroethane. The evolution of reflex (331) for the 95Ni–5Pd sample treated under the reaction conditions has revealed the formation of the interstitial solid solution phase NixPd1–xCδ. According to data of scanning electron microscopy, the formation of separated particles active in carbon growth takes place by 18th minute of exposure with the reaction mixture. After 60 min of interaction the bulk Ni–Pd alloy undergoes complete disintegration with formation of dispersed active centers sized in a range of 0.4–0.6 μm. The elemental mapping of the formed particles showed that palladium is uniformly distributed within the bulk of active particles. The obtained carbon product is represented by ...

Introducing of a New Bio-inspired Hierarchical Porous Silica as an Inorganic Host for Ni–Pd Alloy Nanoparticles for the Synthesis of Aminobiphenyls from the One-Pot Suzuki–Miyaura Coupling-Nitro Reduction

This work reports a facial way to synthesize of an efficient catalyst based Ni–Pd alloy nanoparticles which supported on a new bio-inspired hierarchical porous silica and its catalytic activity in the one-pot Suzuki–Miyaura cross coupling-nitro reduction. The synthesized catalyst was fully characterized by FT-IR, XRD, FESEM–EDX, elemental mapping, TEM, ICP-AES, N2 adsorption–desorption, DRS–UV–Vis and XPS techniques. Use of inexpensive catalyst, high yields of the products and reusability of the catalyst are some of the advantages of our procedure.

Hydrogenation of 2-ethylanthraquinone with bimetallic monolithic catalysts: An experimental and DFT study

We studied the hydrogenation of 2-ethylanthraquinone (eAQ) over Pd/SiO2/COR (COR = cordierite) monometallic and Pd-M/SiO2/COR (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts, which were prepared by the co-impregnation method. Detailed investigations showed that the particle sizes and structures of the Pd-M (M = Ni, Fe, Mn, and Cu) bimetallic monolithic catalysts were greatly affected by the second metal M and the mass ratio of Pd to the second metal M. By virtue of the small particle size and the strong interaction between Pd and Ni of Pd-Ni alloy, Pd-Ni bimetallic monolithic catalysts with the mass ratio of Pd/Ni = 2 achieved the highest H2O2 yield (7.5 g/L) and selectivity (95.3%). Moreover, density functional theory calculations were performed for eAQ adsorption to gain a better mechanistic understanding of the molecule-surface interactions between eAQ and the Pd(1 1 1) or PdM(1 1 1) (M = Ni, Fe, Mn, and Cu) surfaces. It was found that the high activity of the bimetallic Pd-Ni catalyst was a result of strong chemisorption between Pd3Ni1 (1 1 1) and the carbonyl group of eAQ.

Electrodeposition of a Pd-Ni/TiO2 Composite Coating on 316L SS and Its Corrosion Behavior in Hot Sulfuric Acid Solution

Pd-Ni/TiO2 composite coatings were elaborated on 316L stainless steel by an electrodeposition method. The specimens were obtained from an electrolytic bath that contained various contents (5, 10, and 15 g L−1) of nanosized TiO2 particles. X-ray diffraction (XRD) characterization showed that increasing the TiO2 content in the coatings can decrease the crystal grain size. The surface morphology and chemical composition of the composite coatings were modified by the addition of TiO2 particles in the electrolyte, as shown by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) methods, respectively. The TiO2 content also significantly affected the mechanical and electrochemical properties of the Pd-Ni/TiO2 composite coatings. The microhardness of the Pd-Ni/TiO2 composite coatings can be enhanced by increasing the TiO2 content in the coatings. With the addition of 5 g L−1 TiO2 particles to the electrolyte, the deposited Pd-Ni/TiO2 composite coating presented a remarkably increased corrosion resistance when exposed to a sulfuric acid solution at 60 °C compared with that of the Pd-Ni alloy coating. Nevertheless, the further addition of TiO2 particles into the electrolytic bath did not further improve the corrosion resistance of the composite coating.

(Invited) Retrospective on Oxygen Reduction Electrocatalyst R&D Supported By the U.S. Department of Energy

Fuel cells are highly efficient energy conversion devices; they can operate on fuels such as natural gas, methane, and methanol as well as hydrogen generated using diverse domestic resources. Fuel cells are efficient, scalable, and can be used in a variety of applications - from the transportation sector to the generation of primary and secondary power. The U.S. Department of Energy’s (DOE's) Hydrogen and Fuel Cell Program supports early-stage research and development leading to energy security and resiliency, paving the way to a strong domestic economy. Because reducing cost and increasing durability remain as the major challenges in the advancement of fuel cell technology, early-stage R&D includes improvements in performance and durability and lower cost catalysts as well as membrane electrode assemblies for fuel cells and electrolyzers. This presentation will describe the development of oxygen reduction catalysts for fuel cells focusing on the tremendous achievements from Dr. Adzic of Brookhaven National Laboratory. His association with DOE's Office of Energy Efficiency and Renewable Energy began in 2003 with the introduction of Platinum Monolayer Electrocatalysts and was extended to the broader concept of core-shell catalysts. As just a single recent example of the promise of the catalysts, Dr. Adzic and his team recently found that nitriding core components, such as NiPd alloy, in core-shell electrocatalysts resulted in a 50% reduction in Pd content compared to extant Pt/Pd/C catalysts and enhanced overall stability and activity. As a whole, the core shell catalysts have captured the attention of the industry and beyond resulting in U.S. patents, some of which have been licensed to catalyst producers. Other research groups have adopted BNL's concept of core-shell catalysts as well as the use of gold for increasing durability in catalysts. Not surprisingly, R&D 100 and many other awards have followed.

The Electronic Structures of Nickel-Palladium Alloy Clusters: A Density Functional Theory Study

The structure of nickel-palladium (Ni-Pd) alloy clusters of the form NixPdy, where x + y = 7, 13, 55, and 147, and y = x-1, was determined using density functional theory (DFT). For the 7- and 13-atom clusters the lowest energy structures are those that maximize the number of Ni-Pd interactions and they behave as quantum dots. For the 55- and 147-atom clusters, the segregated structure is the most stable isomer and they exhibit metallic character.

Estimation of Transformation Temperatures in Ti–Ni–Pd Shape Memory Alloys

The present study focused on estimating the complex nonlinear relationship between the composition and phase transformation temperatures of Ti–Ni–Pd shape memory alloys by artificial neural networks (ANN). The ANN models were developed by using the experimental data of Ti–Ni–Pd alloys. It was found that the predictions are in good agreement with the trained and unseen test data of existing alloys. The developed model was able to simulate new virtual alloys to quantitatively estimate the effect of Ti, Ni, and Pd on transformation temperatures. The transformation temperature behavior of these virtual alloys is validated by conducting new experiments on the Ti–rich thin film that was deposited using multi target sputtering equipment. The transformation behavior of the film was measured by varying the composition with the help of aging treatment. The predicted trend of transformational temperatures was explained with the help of experimental results.

Room-Temperature Total Hydrogenation of Biomass-Derived Furans and Furan/Acetone Aldol Adducts over a Ni–Pd Alloy Catalyst

Transformation of biomass and its derived compounds to produce fuel and different valuable chemicals is one of the best ways to reduce global dependence on fossil resources. For the production of different value added chemicals seeking application in transportation and various industrial processes, furans are getting much attention owing to the presence of highly reactive −CHO and/or −CH2OH with a furan ring. Here we show a simple yet efficient catalytic strategy for the room-temperature total hydrogenation of biomass-derived furans and their aldol adducts. We describe hydrogenation of different functional groups (furan ring, olefins, and carbonyl groups) of the biomass-derived furans over simple, cost-effective, and highly active bimetallic NiPd alloy nanoparticles at 298 K using a H2 balloon. This procedure is suitable for the hydrogenation of a series of furans and furan/acetone aldol adducts having C5–C15 carbon chains and for a gram-scale transformation for a practical application.