Pd Sn Research Articles

Palladium–Tin Alloyed Catalysts for the Ethanol Oxidation Reaction in an Alkaline Medium

In this paper, we present a study of a series of carbon-supported Pd–Sn binary alloyed catalysts prepared through a modified Polyol method as anode electrocatalysts for direct ethanol fuel cell reactions in an alkaline medium. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy were used to characterize the Pd–Sn/C catalysts, where homogeneous Pd–Sn alloys were determined to be present with the surface Sn being partially oxidized. Among various Pd–Sn catalysts, Pd86Sn14/C catalysts showed much enhanced current densities in cyclic voltammetric and chronoamperometric measurements, compared to commercial Pd/C (Johnson Matthey). The overall rate law of ethanol oxidation reaction for both Pd86Sn14/C and commercial Pd/C were also determined, which clearly showed that Pd86Sn14/C was more favorable in high ethanol concentration ...

Highly effective photocatalytic system comprising semiconductor photocatalyst and supported bimetallic non-photocatalyst for selective reduction of nitrate to nitrogen in water

Photocatalytic reduction of NO3− under UV irradiation in the presence of ethanol was carried out in the presence of semiconductor photocatalyst Pt/TiO2 and supported bimetallic non-photocatalyst Sn–Pd/Al2O3, which were dispersed in water. This system effectively and selectively promoted the photocatalytic reduction of NO3− to N2, whereas Pt/TiO2 or Sn–Pd/Al2O3 alone showed no or little activity under the reaction conditions. The decomposition rate of NO3− and selectivity to gaseous nitrogen compounds (mainly N2) for the present photocatalytic system were higher than those for TiO2 photocatalyst directly-modified with Sn–Pd particles.

Assessment of B3LYP combined with various ECP basis sets for systems containing Pd, Sn, and Pb

An assessment of the performance of various effective core potential (ECP) basis sets for Pd, Sn, and Pb has been presented in this work. In order to carry out this assessment, for a series of diatomic molecules containing Pd, Sn, Pb (the mono- and bimetallic diatomics, as well as the monohydrides and monocarbides of these metals) the values of their three fundamental spectroscopic constants (bond length, harmonic vibrational frequency, dissociation energy) were calculated using the B3LYP density functional combined with nineteen mixtures of ECP basis sets for Pd, Sn, and Pb and with 6-311G(d,p) for H and C. The statistical comparison of the calculated values with the experimental data available allowed us to assess the performance of the considered mixtures of ECP basis sets assigned to the Pd, Sn, and Pb atoms. B3LYP in conjunction with LANL2TZ(f) for Pd, LANL08d for Sn and Pb, and 6-311G(d,p) for H and C provides a sensible compromise between accuracy and computational cost. We believe that this computational approach will be suitable for the future investigations of the semihydrogenation of alkynes on the Pd–Sn and Pd–Pb catalysts.

First example of a heterobimetallic ‘Pd–Sn’ catalyst for direct activation of alcohol: efficient allylation, benzylation and propargylation of arenes, heteroarenes, active methylenes and allyl-Si nucleophiles

Arenes, heteroarenes, 1,3-dicarbonyls and organosilicon nucleophiles undergo highly efficient alkylation with allylic, propargylic and benzylic alcohols in the presence of a new 'Pd-Sn' bimetallic catalyst in nitromethane; water being the sole byproduct. The plausible mechanism of alkylation and the intermediacy of ether has been enumerated.

ChemInform Abstract: New Mixed Palladium—Lead and Palladium—Tin Tellurides of the NiAs Type.

AbstractNew phases of the Pd—Pb—Te and Pd—Sn—Te systems belonging to the NiAs structure type are synthesized from the elements (750 °C, 8—10 h) and characterized by powder XRD.

Optimization of the Pd–Sn–GNS nanocomposite for enhanced electrooxidation of methanol

Highly dispersed Pd nanoparticles with varying loadings (15–40 wt%) and (20 − x)%Pd– x%Sn (where x = 1, 2, 3 and 5) nanocomposites are obtained on graphene nanosheets (GNS) by a microwave-assisted ethylene glycol (EG) reduction method for methanol electrooxidation in alkaline solution. The electrocatalysts were characterized by XRD, SEM, TEM, cyclic voltammetry, and chronoamperometry. The study shows that the Pd nanoparticles on GNS are crystalline and follow the face centered cubic structure. Introduction of a small amount of Sn (1–5 wt%) shifts the characteristic diffraction peaks for Pd slightly to a lower angle. The electrocatalytic performance of the Pd/GNS electrodes has been observed to be the best with 20 wt% Pd loading; a higher or lower loading than 20 wt% Pd produces an electrode with relatively low catalytic activity. The apparent catalytic activity of this active electrode at E = −0.10 V is found to improve further by 79% and CO poisoning tolerance by 40% with introduction of 2 wt% Sn. Among the electrodes investigated, the 18%Pd–2%Sn/GNS exhibited the greatest electrocatalytic activity toward methanol electrooxidation.

Electrochemical preparation of Pt-based catalysts on carbon paper treated with Sn sensitization and Pd activation

CoRuPt and CoPtRu catalysts were prepared on carbon paper (CP) using various electrochemical processes including Sn sensitization, Pd activation, Co electrodeposition and galvanic displacement. The Sn–Pd process is a surface treatment that guarantees a larger number of nucleation sites on CP for subsequent Co electrodeposition by modifying the surface to be more hydrophilic. Co particles were deposited on Sn-Pd-treated CP (SCP) by controlling deposition potential and time. Then, Pt and Ru galvanic displacements were performed on the Co particles to form CoRuPt/SCP and CoPtRu/SCP catalysts. Electrochemical measurements confirmed that the CoRuPt/SCP – 1 catalyst with a 1.02 Pt/Ru surface molar ratio showed a peak potential of 741 mV (vs. NHE) for methanol oxidation and 637 mV for carbon monoxide stripping. These values were 80 and 8 mV lower, respectively, than those of a PtRu/C commercial catalyst.

Dimorphic LaPdSn and ErAgSn – A first principles study

The stannides LaPdSn (orthorhombic TiNiSi type, Pnma) and ErAgSn (hexagonal NdPtSb type, P6 3 mc) both transform to ZrNiAl type ( P – 6 ¯ 2 m ) high-pressure phases with different transition metal-tin ordering. The electronic structure and the chemical bonding of all four modifications have been studied by quantum theoretical DFT methodologies. Geometry optimizations are in good agreement with the experimentally determined structures. Strongest bonding interactions were observed for Pd–Sn (LaPdSn) and Er–Sn (ErAgSn). These findings result from different site occupancies and the chemical natures and electronegativities of the interacting species forming the prevailing chemical bonds in the NP/HP varieties of the two compounds.

The relationship between the structural properties of bimetallic Pd–Sn/SiO 2 catalysts and their performance for selective citral hydrogenation

The effect of Sn addition to Pd on the selective liquid-phase hydrogenation of citral to α,β-unsaturated alcohols (UA: nerol and geraniol) was examined. Pd–Sn/SiO 2 bimetallic catalysts were prepared by successive impregnation method and were characterized by transmission electronic microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDX), temperature-programmed reduction (TPR), Fourier transform infrared (FTIR) spectroscopy of adsorbed CO, and X-ray photoelectron spectroscopy (XPS). Sn addition to Pd/SiO 2 catalysts significantly modifies their properties for citral hydrogenation performed at 130 °C, under 7 MPa and in isopropanol solvent, inducing a promoting effect on the UA selectivity. This promoting effect is related to the existence of a Pd–Sn interaction highlighted by EDX analysis, TPR under hydrogen and FTIR of adsorbed CO. The latter technique suggested the presence of a geometric effect on catalytic activity. Maximum UA selectivities (>75% at 30% citral conversion) were obtained when an alloy of the Pd 3Sn type is formed in the bimetallic particles, as confirmed by TPR and XPS. Moreover, FTIR measurements of the adsorbed CO singleton frequency as well as XPS binding energy shifts strongly imply an electron transfer from Sn to Pd, which is proposed to be responsible for enhanced adsorption of citral C O bond on the surface of Pd–Sn/SiO 2 bimetallic catalysts. To our knowledge, it is the first time that modified Pd catalysts lead to such important UA selectivity values during α,β-unsaturated aldehyde hydrogenation.

Aerosol based fabrication of a Cu/polymer and its application for electromagnetic interference shielding

The effect of a catalytic surface activation on the electromagnetic interference shielding of Cu deposited polymer substrates was investigated. The surface of polymer substrates was catalytically activated by different methods respectively adopted Pd aerosol nanoparticles and Sn–Pd wet chemical processes. Although both activations initiated the deposition of Cu on the substrates, differences such as morphology (Pd aerosol: ~80 nm vs Sn–Pd: ~ 140 nm, in Cu grain size) and composition (Pd aerosol: Cu and Pd vs Sn–Pd: Cu, Pd, Sn, and Cl) of Cu deposits were presented. Specimens activated using Pd aerosol nanoparticles showed a higher range of shielding effectiveness by about 4–10 dB than those activated by Sn–Pd processes in 2–18 Ghz frequencies.

Pd3Sn8Bi6]4–: A 14-Vertex Sn/Bi Cluster Embedding a Pd3 Triangle

The endohedral cluster anion [Pd(3)Sn(8)Bi(6)](4-) crystallizes as its K([2.2.2]crypt)(+) salt 1 upon reaction of [K([2.2.2]crypt)](2)[Sn(2)Bi(2)]·en and Pd(dppe)(2) in 1,2-diaminoethane (en)/toluene and incorporates a complete Pd(3) triangular cluster within a medium-size 14-vertex cage of Sn and Bi atoms. 1 was characterized by a combination of single crystal diffraction, ESI mass spectrometry, elemental analysis, and magnetic measurements. According to quantum chemical investigations, the Pd(3) triangle interacts only weakly with the Sn/Bi cluster shell despite the relatively small cavity inside the cage.

Influence of Cu2O surface treatment on the photovoltaic properties of Al-doped ZnO/Cu2O solar cells

Low cost Al-doped ZnO (AZO)/Cu2O Schottky barrier solar cells with a high conversion efficiency of 2.19% were fabricated by depositing a transparent conducting AZO thin film on high quality Cu2O sheets prepared by thermally oxidizing copper sheets. To achieve efficiencies higher than 2%, it is necessary to form the AZO thin film at a low deposition temperature using a low-damage deposition method, i.e., at room temperature by a pulsed laser deposition. In addition, the obtained efficiency could be enhanced with a surface treatment of the Cu2O sheets, such as by applying a Pd–Sn catalyst layer as a coating or a rapid thermal annealing treatment at approximately 500°C in air.

Preparation and characterization of negative thermal expansion Sc 2W 3O 12/Cu core–shell composite

A composite of Sc 2W 3O 12/Cu where Sc 2W 3O 12, the core, is coated by the Cu shell was synthesized using simple electroless plating method. As-prepared Sc 2W 3O 12/Cu composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and thermomechanical analyzer (TMA) techniques. The study results show that the Pd–Sn activator was successfully formed on the surface of Sc 2W 3O 12 after the sensitization and activation. In the electroless plating process, Cu nanocrystals formed firstly, and then grew together to form a continuous coating. Sc 2W 3O 12/Cu core–shell composites exhibit a negative linear coefficient of thermal expansion CTE = −4.47 × 10 −6 °C −1 from room temperature to 200 °C.

Mineralogy, geochemistry and stratigraphy of the Maslovsky Pt–Cu–Ni sulfide deposit, Noril’sk Region, Russia

We report new data on the stratigraphy, mineralogy and geochemistry of the rocks and ores of the Maslovsky Pt–Cu–Ni sulfide deposit which is thought to be the southwestern extension of the Noril’sk 1 intrusion. Variations in the Ta/Nb ratio of the gabbro-dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses, which gave rise to the Northern and Southern Maslovsky intrusions that together host the Maslovsky deposit. The Northern intrusion is located inside the Tungusska sandstones and basalt of the Ivakinsky Formation. The Southern intrusion cuts through all of the lower units of the Siberian Trap tuff-lavas, including the Lower Nadezhdinsky Formation; demonstrating that the ore-bearing intrusions of the Noril’sk Complex post-date that unit. Rocks in both intrusions have low TiO2 and elevated MgO contents (average mean TiO2 <1 and MgO = 12 wt.%) that are more primitive than the lavas of the Upper Formations of the Siberian Traps which suggests that the ore-bearing intrusions result from a separate magmatic event. Unusually high concentrations of both HREE (Dy+Yb+Er+Lu) and Y (up to 1.2 and 2.1 ppm, respectively) occur in olivines (Fo79.5 and 0.25% NiO) from picritic and taxitic gabbro-dolerites with disseminated sulfide mineralization. Thus accumulation of HREE, Y and Ni in the melts is correlated with the mineral potential of the intrusions. The TiO2 concentration in pyroxene has a strong negative correlation with the Mg# of both host mineral and Mg# of host rock. Sulfides from the Northern Maslovsky intrusion are predominantly chalcopyrite–pyrrhotite–pentlandite with subordinate and minor amounts of cubanite, bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals (Au, Ag and Pd), Sn–Pd–Pt–Bi–Pb compounds and Fe–Pt alloys. Sulfides from the Southern Maslovsky intrusion have δ34S = 5–6‰ up to 10.8‰ in two samples whereas the country rock basalt have δ34S = 3–4‰, implying there was no in situ assimilation of surrounding rocks by magmas.

A study of different supports for the catalytic reduction of nitrates from natural water with a continuous reactor

The aim of this work is to study the activity for the nitrate catalytic reduction in natural water, using a continuous stirred tank reactor, of Pd/Cu and Pd/Sn catalysts supported on different materials. The studied supports are: γ-Al2O3 (commercial), active carbon, graphite, hydrotalcite and alumina synthesized in our laboratory with a high surface area. The activity and selectivity of the catalysts supported on these materials have been compared. The best results have been obtained with the Pd/Sn catalysts supported on alumina. These results show that the surface area of the support is not the only important characteristic for an active catalyst in this reaction, but also its acid–base properties, electrical conductivity and interaction with the metallic active sites are very significant. The adequate combination of these characteristics is necessary to obtain an active catalyst. The influence of the Pd/Sn content on the activity of the alumina supported catalysts was studied, observing that the best activity was obtained when the Pd/Sn ratio was higher than 1. This result clearly indicates that it is necessary to have both Pd and Pd–Sn centers in order to obtain an active catalyst.

Effects of Pd concentration on the interfacial reaction and mechanical reliability of the Sn–Pd/Ni system

The liquid–solid reaction between Sn– xPd alloy and Ni ( x = 0.05–1 wt.%) and the resulting mechanical reliability of the system were examined in this study. The reactions strongly depended on the Pd concentration and the reaction time. When the Pd concentration was low (i.e., x = 0.05 wt.%), the reaction product was only Ni 3Sn 4. In contrast, when the Pd concentration was high (i.e., x ≥ 0.2 wt.%), the reaction product became a dual-layer structure of (Pd,Ni)Sn 4–Ni 3Sn 4. Between 0.05 wt.% and 0.2 wt.% (e.g., x = 0.1 wt.%), discontinuous (Pd,Ni)Sn 4 grains scattered over the Ni 3Sn 4 layer developed. Interestingly, the (Pd,Ni)Sn 4 grains were gradually dispersed in the molten Sn–Pd alloy, leaving the Ni 3Sn 4 at the interface, as the reaction time increased. These Pd-dependent reactions were dictated by thermodynamics and can be rationalized using the Pd–Ni–Sn isotherm. Furthermore, the results of the high-speed-ball-shear (HSBS) test indicated that the mechanical strength of the Sn–Pd/Ni joints dramatically degraded by over one third due to the formation of (Pd,Ni)Sn 4 at the interface. The implication is that the Pd concentration in Sn–Pd solder joints should be reduced to a level below 0.2 wt.% to prevent the creation of an undesired microstructure.

Stannylene or Metallastanna(IV)ocane: A Matter of Formalism

Pushmi-pullyu with palladium: Although created by σ donation from SnCl2 to a PdII complex, the SnPd bonds in the compounds depicted exhibit formal σ donation in the opposite direction. Computational and spectroscopic data support stannylpalladium (PdISnIII) and palladastanna(IV)ocane (Pd0→SnIV) descriptions over stannylene coordination.

Crystal and electronic structure of LaPdSn and RE3Pd 4Sn 6 ( RE = La, Ce)

The stannide LaPdSn has been synthesized by arc-melting and the structure has been refined from X-ray single crystal diffractometer data: TiNiSi type, Pnma, a = 763.8(1), b = 473.47(7), c = 799.4(1) pm, wR2 = 0.0417, 548 F 2 values, 20 variables. The electronic structures of LaPdSn, La 3Pd 4Sn 6 and Ce 3Pd 4Sn 6 (own type) were investigated through scalar relativistic all-electron calculations within the DFT framework. The three stannides show a weakly metallic behavior with itinerant states crossing the Fermi level. The chemical bonding strength is such that Pd–Sn > La(Ce)–Sn > La(Ce)–Pd with a relevant feature of significant Sn–Sn bonding in La 3Pd 4Sn 6, in agreement with the interatomic distances in the [PdSn], respectively [Pd 4Sn 6] polyanions. Spin polarized calculations on Ce 3Pd 4Sn 6 show spin polarization on all three crystallographically independent cerium sites, leading to ferrimagnetism.

New mixed palladium—lead and palladium—tin tellurides of the NiAs type

New ternary mixed nickel arsenide-type palladium and platinum—Group 14 metal tellurides were searched for by the high-temperature ampoule synthesis combined with the X-ray powder diffraction analysis. As a result, new phases of the ternary Pd—Pb—Te and Pd—Sn—Te systems belonging to the NiAs structure type were synthesized. The crystal structure of the compound PdPb0.304(5)Te0.695(5) was determined by the Rietveld method (P63/mmc, a = 4.151(1) A, c = 5.680(1) A, Z = 2, R1 = 0.032, Rp = 0.075, wRall = 0.025). It was shown that no ordering exists in the occupancy of the main-group atom site by lead and tellurium. In the Pd—Sn—Te system, a phase isostructural with the above-mentioned compound was found. In the latter phase, there is also no ordering in the occupancy of the main-group atom site. According to the electron diffraction data, a superstructure derived from the NiAs type exists in a narrow range of the compositions PdSn0.3Te0.7—PdSn0.4Te0.6.

Carbon supported Pd–Sn and Pd–Ru–Sn nanocatalysts for ethanol electro-oxidation in alkaline medium

Carbon supported Pd–Sn and Pd–Ru–Sn nanocatalysts were prepared by the chemical reduction method, using sodium borohydride and ethylene glycol mixture as the reducing agent. The catalytic activity towards ethanol electro-oxidation in alkaline medium was studied by cyclic, carbon monoxide stripping voltammetries and chronoamperometry. The current density obtained for the electro-oxidation was affected by varying ethanol concentration between 0.25 and 4 M. Raising ethanol concentration up to 3 M increased the coverage of the adsorbed ethoxy (CH 3CO ads) species on the nanocatalyst surface, thus yielding an increase in current density. Pd–Sn/C displayed better electrocatalytic activity and stability towards poisoning than Pd–Ru–Sn/C and Pt–Ru/C (E-TEK Inc.) nanocatalysts. Transmission electron microscopy results showed that Pd–Sn and Pd–Ru–Sn nanoparticles were uniformly dispersed on carbon support. The average particle size of Pd–Sn was 7 ± 0.5 nm in diameter while for Pd–Ru–Sn was 6 ± 0.7 nm.