Pd Ratio Research Articles

Combining the core-shell construction with an alloying effect for high efficiency ethanol electrooxidation

Summary Combining core-shell construction with an alloying effect is effective for optimizing the electronic and lattice strain effects for achieving highly catalytic efficiency for a given electrochemical reaction. Here, we report the use of core-shell Au@FePd nanoparticles with an Au core and a sub-nano FePd alloy shell to demonstrate this concept. The Au core modifies the electronic configuration of Pd atoms, while the Fe component in thin shells reduces the lattice expansion of Pd induced by the Au core, both of which endow the Pd shell with an appropriate d-band center, favorable for the electrooxidation of ethanol through the C1 pathway. In particular, the as-prepared core-shell Au@FePd nanoparticles at an optimized Fe:Pd ratio exhibit a mass activity of 13.3 A mg−1 and a specific activity of 20.2 mA cm−2 for the ethanol electrooxidation in an alkaline medium, which outperform those of a majority of the recently reported Pd-based electrocatalysts.

Superior catalytic activity of Pd-based catalysts upon tuning the structure of the ceria-zirconia support for methane combustion

Pd-based catalysts supported on CeO2-ZrO2 (CZ) mixed oxides have been universally applied toward the oxidation of methane, a strong greenhouse gas. Herein, CZ supports of different structures were prepared using hydrothermal (ST-CZ), co-precipitation (CP-CZ), and physical mixing (Mix-CZ) methods. Subsequently, the effects of the CZ support structure on the catalytic activity of the resulting Pd/CZ catalysts toward methane combustion were evaluated. ST-CZ shows the presence of cubic and tetragonal phases of CZ solid solutions, while CP-CZ is a pure tetragonal-phase solid solution and Mix-CZ is a mixture of CeO2 and ZrO2. The CZ solid solution improved the Pd dispersion and Pd2+/Pd ratio on the catalyst surface. Furthermore, CZ oxides with a two-phase composite structure resulted in higher oxygen storage capacity and oxygen mobility in the Pd/CZ catalysts than in the pure solid solution phase. Therefore, the Pd/ST-CZ catalyst shows superior catalytic activity for methane combustion than the other two catalysts.

Hydrodeoxygenation of benzofuran on novel CoPdP catalysts supported on potassium ion exchanged ultra-stable Y-zeolites

The synthesis of bimetallic CoPdP phosphides supported on potassium ion exchanged ultra-stable Y (KUSY) zeolites was studied and catalytic activity tests on the hydrodeoxygenation of a model pyrolysis oil compound, benzofuran, were conducted. Temperature programmed reduction (TPR) profiles revealed that Pd aided the reduction of the Co, lowering both the onset and peak temperatures for reduction. The catalyst structure was probed by X-ray diffraction (XRD) and extended X-ray adsorption fine structure (EXAFS), which showed the formation of CoPdP alloys. Fourier-transform infrared spectroscopy was used to probe the Co and Pd sites on the surface. Several Co:Pd ratios were tested in the range of 225–350 °C at a medium pressure of 0.5 MPa. Synergistic effects were observed between Co and Pd, with the alloys showing higher activity than the single metal Pd or Co phosphide catalysts. High selectivity to unsaturated high carbon number products were obtained for the bimetallic phosphide catalysts.

Core-Shell AgPdPt Composite Catalyst Advanced Electrochemical Activity

Three kinds of tri-metallic catalysts with core–shell structure are synthesized, in which the outer shell is alloy of Pt and Ag, and the inner core consists of Ag and Pd. Amongst, the composite catalyst with atomic ratio of Ag, Pd and Pt equaling to 1:1.4:1.2 (denoted as Ag1Pd1.4Pt1.2) has the greatest total mass activity (3310.7 mA mgmetal −1), which is much higher than commercial Pt-Ru, Pt- and Pd-based catalysts reported previously. The superior catalytic activity for methanol oxidation should be due to the high amount of Pt alloyed with the least Ag in outer shell and boundary of PtAg outer shell and AgPd inner core composed of tiny nanoclusters, endowing synergistic effect from the electronic structure, numerous defeats, and available great internal and external surface areas. In addition, Ag1Pd1.4Pt1.2 catalyst about 250 nm at mesoscopic scale shows improved stability to large extent. Meanwhile, the presence of Pd in Ag1Pd1.4Pt1.2 contributes outstanding ability against CO poisoning. This work may pave a promising way to prepare core–shell composite catalyst with high catalytic performance for fuel cell application.

Extraction of rhenium(VII) and palladium(II) from nitric acid solution using N-cyclohexyl-2-pyrrolidone as an extractant

ABSTRACT Extraction behavior of Pd(II) and Re(VII) from HNO3 aqueous solutions (0.1–5.0 M, M = mol∙dm−3) to CH2Cl2 containing N-cycrohexyl-2-pyrrolidone (NCP, 0.1–2.0 M) as an extractant has been examined. As a result, it was found that distribution ratios (D) of Pd(II) and Re(VII) under [HNO3] = 3.0 M increase with increasing [NCP] from 0.1 to 2.0 M and that plots of log D vs. log[NCP] show linear relationships with slopes of approximately 2. It was also found that the D values for Pd(II) increase with increasing [HNO3] up to 3.0 M and decrease in the higher [HNO3] region (<5.0 M) and those of Re(VII) increase with an increase in [HNO3] up to 1.0 M and decrease with a further increase in [HNO3] (<5 M). From these results, it was suggested that the extraction reactions of Pd(II) and Re(VII) take place with two NCP molecules and compete with the extraction of HNO3. Moreover, it was clarified that IR spectra (1550–1700 cm−1) of CH2Cl2 solutions containing extracted Pd(II) and Re(VII) species are consistent with that of trans-Pd(NO3)2(NCP)2 and similar to that of HReO4(NCP)2, respectively. From these results, it is proposed that Pd(II) and Re(VII) species in HNO3 aqueous solutions are extracted to CH2Cl2 phase containing NCP as Pd(NO3)2(NCP)2 and HReO4(NCP)2.

NickelPalladium alloy–reduced graphene oxide as counter electrode for dye-sensitized solar cells

In this work, nickel-palladium (NiPd) alloy-reduced graphene oxide (rGO) has been prepared via liquid-phase deposition (LPD) technique and applied as counter electrode (CE) of dye-sensitized solar cell (DSSC). The effect of Ni content on the properties of the sample and the performance of the device utilizing the CE has been investigated. The morphology of the sample is described by rumples and white strips distributed on the ITO surface. The device utilizing the CE prepared with the Ni:Pd ratio of 20:1 owns the highest power conversion efficiency (η) of 2.13%. This is due to this device possesses the lowest series resistance (Rs) of 84.6 Ω and the highest incident photon conversion efficiency (IPCE) of 11.30%. The findings of this work reveal that NiPd-rGO has potential to substitute platinum (Pt) as CE of DSSC since its η is comparable to that of Pt based device.

Pd-Pt Tesseracts for the Oxygen Reduction Reaction.

Hollow frame structures are of special interest in the realm of catalysis since they hold only ridges and hollow interiors, enabling the accessibility of active sites to the most extent. Herein, we prepared Pd-Pt hollow frame structures composed of double-shell cubes linked by body diagonals as an efficient catalyst toward the oxygen reduction reaction (ORR), inspired by the 4D analogue of a cube, denoted as a tesseract. The etching process involves the selective removal of Pd atoms and the subsequent rearrangement of the remaining Pd and Pt atoms. The successful preparation of Pd-Pt tesseracts via etching lies in the selection of Pd/Pt ratio in the initial Pd-Pt nanocubes. With various ratios of Pd-Pt nanocubes as templates, we obtained Pd-Pt octapods, tesseracts, and nanoframes, respectively. During the ORR, Pd-Pt tesseracts exhibited the highest mass activity of 1.86 A mg-1Pt among these Pd-Pt nanocrystals. On the basis of mechanistic studies, the high activity of Pd-Pt tesseracts derived from the optimal oxygen adsorption energy due to the facet effect and composition effect.

Bimetallic RuPd nanoparticles in ionic liquids: selective catalysts for the hydrogenation of aromatic compounds

Bimetallic RuPd nanoparticles are effective catalysts for the hydrogenation of aromatic compounds and the activity and selectivity depend on the Ru : Pd ratio.

α-Substituted phthalocyanines based on metal-induced H- or J-type aggregation for silver and palladium ions: synthesis, fluorescence, and antimicrobial and antioxidant properties.

In this study, firstly, 3-(2,3-bis(hexadecylthio)propoxy)phthalonitrile (2) as a new phthalonitrile derivative was prepared. Then, new types of non-peripheral phthalocyanine derivatives [CuPc (3), ZnPc (4), and CoPc (5)] were synthesized by using this ligand. The synthesized new compounds were characterized by common spectroscopic methods such as FTIR, 1H-NMR, 13C-NMR, MALDI-TOF, UV-Vis and fluorescence spectroscopy. The H- or J-type aggregation behaviors of novel type metallophthalocyanines in the presence of valuable metal ions such as Ag(i) and Pd(ii) were investigated by UV-Vis and fluorescence spectroscopy. The quenching efficiency of the Ag(i) and Pd(ii) ions for ZnPc (4) was obtained using the Stern-Volmer equation and the quenching constant of ZnPc (4) towards Ag(i) and Pd(ii) ions was found to be 2.9 × 105 mol L-1 and 1.2 × 105 mol L-1, respectively. The binding constant (Ka) and binding stoichiometry (n) of Ag(i) and Pd(ii) ions for ZnPc (5) were calculated using a modified Benesi-Hildebrand equation, and were found to be 1.4 × 108 M-1 and 3.4 × 107 M-1, respectively. The binding ratio and free energy change of Ag(i) and Pd(ii) ions for ZnPc (4) were found to be 1.86, 1.54, -46.49 kJ mol-1 and -42.9 kJ mol-1, respectively. Also, the antioxidant properties of the synthesized novel type metallophthalocyanines and their Ag(i) and Pd(ii) ion doped aggregates were determined using three different methods: DPPH free radical scavenging activity, ferrous ion chelating activity and reducing power activity. Finally, the antibacterial and antifungal activities of phthalocyanine compounds synthesized within the scope of this study were determined by disc diffusion and macrobroth dilution methods and the effect of the doping of Ag(i) and Pd(ii) ions on the antibacterial activities of phthalocyanines was investigated.

Market Pricing of Fundamentals at the Shanghai Stock Exchange: Evidence from a Dividend Discount Model with Adaptive Expectations

We study market pricing of fundamentals at the Shanghai Stock Exchange, incorporating possible irrational pricing behavior with adaptive expectation. Using panel data of listed stocks to overcome the limited information in aggregate time series data, we estimated key parameters of the price elasticity of dividends and the expectation adjustment based on a linear dynamic panel data model. We use a major subset of stocks with stationary real prices and cash flows and apply methods that correct for incidental parameter bias. The resulting price elasticity of dividends is about 0.46 (0.35) based on annual (quarterly) data, which is sizable given high PD (PE) ratios in the market. Our results imply that slow expectation adjustment contributes to “bubble-like” price patterns. We also show prices significantly react to macro information related to the discount rate, but these effects are very sensitive to the information set used.

Strong metal–support interaction between palladium and gallium oxide within monodisperse nanoparticles: self-supported catalysts for propyne semi-hydrogenation

The strong metal–support interaction (SMSI) between metals and reducible supports (e.g., CeO2, TiO2, and SnO2), which has been widely investigated, plays a very important role in heterogeneous catalysis. We report the first example of SMSI between palladium (Pd) and gallium oxide (Ga2O3) within a PdGa nanoparticle (denoted as PdxGay NP, where x:y is the atomic ratio of Pd and Ga). The typical features of classic SMSI, such as electron transfer between Ga2O3 and Pd and suppression of H2 and CO adsorption, are successfully observed on PdxGay NPs. Detailed characterizations and control experiments demonstrate that the coexistence of PdGa alloy and Ga2O3 in PdxGay NPs plays a vital role in the formation of SMSI. To systematically study the effects of SMSI on catalytic performance, PdxGay NPs were used as “self-supported catalysts” for propyne semi-hydrogenation (PSH), a critical process for removing trace propyne from propylene in industry. It is shown that optimized Pd0.34Ga1 NPs give a propylene selectivity of 98.2% at a propyne conversion of 96.6% at 30 °C and atmospheric pressure, which is much higher than that of pure Pd NPs and Pd/Ga2O3 catalysts prepared by a conventional wet-impregnation method. The reaction paths of PSH on PdxGay NPs have been further revealed by density functional theory (DFT) calculations. This work may not only deepen the basic understanding of SMSI, but also promote the design and application of heterogeneous catalysts.

Preparation of PdAuCu/C as a Highly Active Catalyst for the Reduction of 4‐Nitrophenol by Controlling the Deposition of Noble Metals

AbstractThe reasonable control of the dispersion of noble metals is an important topic for heterogeneous catalysts. In this manuscript, PdCu/C, AuCu/C and PdAuCu/C were prepared by the galvanic reduction method to ensure that Pd and Au follow the distribution of Cu nanoparticles. The catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy‐dispersive spectrometer elemental mappings and lines scans. Both the Pd and Au had very high dispersion no matter whether they were introduced individually or simultaneously. The Pd and Au were distributed mainly on the Cu nanoparticles as evidenced by the energy‐dispersive spectrometer elemental mappings and lines scans. The reduction of 4‐nitrophenol was used as a model reaction for the prepared catalysts. PdCu/C and AuCu/C showed high activity for this reaction compared to the literature, and the activity could be further increased by the introduction of Pd and Au in an appropriate ratio at the same time. The normalized reaction rate reached 2.005 s−1 mM−1 for the PdAuCu/C‐2.0, in which the mole ratio of Pd to Au was 2.0.

Holey PdPb nanosheet array: An advanced catalyst for methanol electrooxidation

Holey PdPb nanosheet array is successfully synthesized using the CO confinement method. By tuning the ratio of Pd to Pb, the optimized holey Pd8Pb nanosheet array exhibits 4.8-fold higher peak current density and better stability toward methanol electrooxidation compared to the commercial Pd/C, holding great promise as an anode catalyst for direct methanol fuel cells.

Magnetic anisotropy of cobalt - palladium CoxPd100-x thin films on amorphous SiO2

Cobalt – palladium thin films with different Co:Pd ratio, CoxPd100-x (x=23, 36, 42), have been deposited on fused silica (amorphous SiO2) by pulsed laser deposition (PLD). For the structural characterization of the thin films, X-ray reflectivity (XRR) and X-ray diffraction (XRD) are used and for investigation the magnetic characteristics of the films, physical properties measurement system (PPMS) is used. The results show that the thickness of the thin films is in the range of 16-20 nm and the crystal structure of the films is FCC. Also, the films have a [111] preferred growth direction. The study of the magnetic properties shows that the magnetic anisotropy tends to align in the perpendicular direction by the increase of Pd:Co ratio, which is attributed to the enhancement of the spin-orbit interaction. Also, in this work, the effect of thickness on the magnetic anisotropy is investigated.

High catalytic performance of a Pd-loaded TaN-TaC electrocatalyst for ethylene glycol oxidation in an alkaline medium

In this work, tantalum nitride and tantalum carbide (TaN-TaC) composites are prepared using a one-step calcination method. The resulting TaN-TaC composites have excellent conductivity, and therefore, potential applications in the electrode materials of fuel cells. Then, palladium nanoparticles loading on TaN-TaC (Pd/TaN-TaC) electrocatalysts are synthesized using the reflux method. The X-ray photoelectron spectroscopy results imply that the valance states of palladium are of the form Pd0 and Pd2+ on the surface of TaN-TaC composites. The electrocatalytic activity of the Pd/TaN-TaC catalysts is measured in a 0.5 mol L−1 KOH solution and 1 mol L−1 of ethylene glycol. These results imply that the Pd/TaN-TaC electrocatalyst modified glassy carbon electrode has a high catalytic activity for ethylene glycol electrooxidation in an alkaline medium. The dosage of Pd is 7% (mass ratio of Pd and TaN-TaC) and it exhibits the higher electrocatalytic activity, and superior to the commercial Pd/C (10%).

Ni-Pd/γ-Al2O3 Catalysts in the Hydrogenation of Levulinic Acid and Hydroxymethylfurfural towards Value Added Chemicals

γ-Al2O3 supported Ni-Pd catalysts with different Ni:Pd ratios were studied in the hydrogenation of two industrially-relevant platform molecules derived from biomass, namely levulinic acid and hydroxymethylfurfural. The bimetallic catalysts showed better performances in both processes in comparison to the monometallic counterparts, for which a too strong interaction with the alumina support reduced the activity. The behavior of the bimetallic catalysts was dependent on the Ni:Pd ratio, and interestingly also on the targeted hydrogenation reaction. The Pd-modified Ni-rich system behaves like pure Ni catalyst, but with a strongly boosted activity due to a higher number of Ni active sites available, Pd being considered as a spectator. This high activity was manifested in the levulinic acid hydrogenation with formic acid used as an internal hydrogen source. This behavior differs from the case of the Pd-rich system modified by Ni, which displayed a much higher Pd dispersion on the support compared to the monometallic Pd catalyst. The higher availability of the Pd active sites while maintaining a high surface acidity allows the catalyst to push the HMF hydrodeoxygenation reaction forward towards the green biopolymer precursor 2,5-bis(hydroxymethyl)-tetrahydrofuran, and in consequence to strongly modify the selectivity of the reaction. In that case, residual chlorine was proposed to play a significant role, while Ni was considered as a spectator.

Predictors of intraocular pressure change after cataract surgery in patients with pseudoexfoliation glaucoma and in nonglaucomatous patients

Background/Aim. The cataract surgery in eyes with and without glaucoma results in the sustained intraocular pressure (IOP) reduction but it is still unknown which glaucomatous patients will achieve clinically significant reduction. The preoperative IOP and some ocular biometric parameters have been shown as potential predictors of the postoperative IOP reduction. The aim of our prospective intervention study was to evaluate that relationship in medically controlled patients with the pseudoexfoliation glaucoma (PXG) and in the nonglaucomatous patients. Methods. Thirty-one PXG patients (31 eyes) and 31 nonglaucomatous patients (31 eyes), all with clinically significant cataract, were enrolled. The preoperative IOP, anterior chamber depth (ACD), axial length (AL), lens thickness (LT), lens position (LP) [LP = ACD + 0.5 LT], relative lens position (RLP) [RLP = LP / AL] and the pressure-to-depth ratio (PD ratio) [PD ratio = preoperative IOP/preoperative ACD] were evaluated as potential predictors of the IOP change in the 6th postoperative month. Results. In the 6th postoperative month, in the PXG group, the IOP reduction was -3.23 ? 3.41 mmHg (-17.67 ? 16.86%) from the preoperative value of 16.27 ? 3.08 mmHg and in the control group, the reduction was -2.26 ? 1.71 mmHg (-15.06 ? 10.93%) from the preoperative value of 14.53 ? 2.04 mmHg. In the PXG group, the significant predictors of the absolute and the percentage IOP reduction were the preoperative IOP, AL, and PD ratio. In the same group, RLP was shown as a significant predictor of absolute change in the IOP in multi-variate analysis, and the percentage IOP change in both the univariate and the multivariate analyses. In the control group, the preoperative IOP and the PD ratio were the only significant parameters that could predict absolute change in the postoperative IOP. Conclusion. The cataract surgery leads to the IOP reduction both in the PXG and nonglaucomatous eye. Predictors monitored in this study are widely available and simply calculable parameters that can be potentially used in managing glaucoma.

Composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles having an average size of 1.7 nm for hydrolytic dehydrogenation of ammonia borane

We investigated composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles (DENs) that had a uniform size of ∼1.7nm for hydrolytic dehydrogenation of ammonia borane (AB). The PtPd DENs, composed of seven different Pt: Pd ratios, were synthesized using hydroxyl-terminated sixth-generation polyamidoamine dendrimers as a molecular template. The dendrimer-templating method allowed for synthesizing bimetallic PtPd DENs with controllable nanoparticle composition while fixing the size of the nanoparticles uniformly at ∼1.7 nm. Compared with monometallic Pt and Pd DENs, the bimetallic PtPd DENs showed superior catalytic activity for the hydrolytic dehydrogenation of AB. Furthermore, the bimetallic PtPd DENs exhibited composition-dependent activity with the maximum activity (i.e., average turnover frequency=108.5±15.9molH2·molatom Pt+pd−1·min−1) at a Pt: Pd ratio of 1:1 for the catalytic hydrolysis of AB.

High Active PdSn Binary Alloyed Catalysts Supported on B and N Codoped Graphene for Formic Acid Electro-Oxidation

A series of PdSn binary catalysts with varied molar ratios of Pd to Sn are synthesized on B and N dual-doped graphene supporting materials. The catalysts are characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Formic acid electro-oxidation reaction is performed on these catalysts, and the results reveal that the optimal proportion of Pd:Sn is 3:1. X-ray photoelectron spectroscopy (XPS) measurements show that when compared with 3Pd1Sn/graphene, B and N co-doping into the graphene sheet can tune the electronic structure of graphene, favoring the formation of small-sized metallic nanoparticles with good dispersion. On the other hand, when compared with the monometallic counterparts, the incorporation of Sn can generate oxygenated species that help to remove the intermediates, exposing more active Pd sites. Moreover, the electrochemical tests illustrate that 3Pd1Sn/BN-G catalyst with a moderate amount of Sn exhibits the best catalytic activity and stability on formic acid electro-oxidation, owing to the synergistic effect of the Sn doping and the B, N co-doping graphene substrate.

Variation in palladium and water quality parameters and their relationship in the urban water environment.

Palladium (Pd) is widely used in vehicle exhaust catalysts (VECs) to reduce toxic emissions from motor vehicles. The study aimed to quantitatively determine Pd content and water quality parameters, to analyze the variation differences and to explore the effect of water quality parameters on Pd content in the urban water environment system (wet deposition-rainfall runoff-receiving water body-estuary) of the city of Haikou, Hainan Island, China. The method used in this study included microwave digestion under high pressure and temperature, analysis by inductively coupled plasma mass spectrometry, quality control of the experimental procedure and guaranteed recovery (85% -125%). The results showed that the dissolved Pd average content in the urban water environment system was the highest in rainfall runoff (4.93 ng/L), followed by that in the receiving water body (4.56 ng/L), and it was the lowest in wet deposition (0.1 ng/L). The suspended Pd average content was the highest in the estuary (2.83 ng/L), followed by that in rainfall runoff (1.26 ng/L), and it was the lowest in wet deposition (6 × 10-4 ng/L). The particle-water partition ratio of the estuary Pd was the highest (1.26), followed by that of Pd in rainfall runoff (0.26). The particle-water partition ratio of the wet deposition Pd was the lowest (6 × 10-3). The dissolved Pd was correlated with the pH, Cl-, and total suspended solids (TSS) (correlation coefficient = 0.52, -0.68, 0.39, p < 0.05; regression coefficient = 1.27, -1.39, 0.01). The suspended Pd was only correlated with Cl- and TSS (correlation coefficient = -0.36, 0.76, p < 0.05; regression coefficient = -1.45, 0.01). Cl- and TSS were the most closely related to Pd in the water environment system. Although individual factors such as pH, Cl-, and TSS had certain migration and transformation effects on Pd in the wet deposition-rainfall runoff-receiving water body-estuary system, the probability of strong correlations was not high. In particular, Eh was not related to the dissolved nor suspended Pd content (correlation coefficient = 0.14, 0.13), which may be due to the synergistic effect of the multiple physical factors on Pd. This study was helpful to better understand the environmental behavior of Pd and provided important theoretical support for the prevention and protection against urban water environmental pollution.