Comparison Of Pt Research Articles

Stability and dissolution of single-crystalline iron oxide thin films in electrochemical environments

The stability of single-crystalline monolayer FeO(111) and 10 nm thin Fe3O4(111) films on Pt(111) upon exposure to environments of increasing chemical complexity has been studied with X-ray photoelectron spectroscopy, temperature-programmed desorption, in-situ scanning tunneling microscopy, and cyclic voltammetry. The well-defined oxide films, which were prepared under ultrahigh-vacuum conditions, were exposed to aqueous solutions of different pH and electrochemical cycling in pure and catechol-containing electrolyte. The films are stable in neutral (pH 7) and alkaline (pH 13) solutions both at open circuit conditions and during electrochemical cycling within the limits of hydrogen and oxygen evolution potentials. Also in strongly acidic (pH 1) perchlorate solution the films remain intact under open circuit conditions, but they quickly dissolve on application of electrochemical potential. Especially for the ultrathin FeO(111) films, catechol enhances the dissolution at neutral pH during electrochemical cycling. A comparison of Pt(111), FeO(111) and Fe3O4(111) substrates in the electrochemical catechol oxidation reaction reveals enhanced and sustained activity of FeO in alkaline environment, while strong deactivation occurs on Pt(111) and Fe3O4(111). This is explained by the weaker interaction between catechol and FeO(111) compared to the other substrates, which hampers the formation of a barrier layer on the electrode surface.

Measurements of jet quenching using semi-inclusive hadron+jet distributions in pp and central Pb-Pb collisions at sNN=5.02 TeV

The ALICE Collaboration reports measurements of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum (high pT) charged hadron, in pp and central Pb-Pb collisions at center-of-mass energy per nucleon–nucleon collision sNN=5.02 TeV. The large uncorrelated background in central Pb-Pb collisions is corrected using a data-driven statistical approach which enables precise measurement of recoil jet distributions over a broad range in pT,chjet and jet resolution parameter R. Recoil jet yields are reported for R=0.2, 0.4, and 0.5 in the range 7<pT,chjet<140 GeV/c and π/2<Δφ<π, where Δφ is the azimuthal angular separation between hadron trigger and recoil jet. The low-pT,chjet reach of the measurement explores unique phase space for studying jet quenching, the interaction of jets with the quark–gluon plasma generated in high-energy nuclear collisions. Comparison of pT,chjet distributions from pp and central Pb-Pb collisions probes medium-induced jet energy loss and intra-jet broadening, while comparison of their acoplanarity distributions explores in-medium jet scattering and medium response. The measurements are compared to theoretical calculations incorporating jet quenching. ©2024 CERN, for the ALICE Collaboration 2024 CERN

Enhanced electrochemical degradation of perfluorooctanoic acid by ligand-bridged PtII at Pt anodes

A new mechanism for the electro-oxidation (EO) degradation of perfluorooctanoic acid (PFOA) by Pt anode was reported. Using bridge-based ligand anions (SCN-, Cl- and N3-) as electrolytes, the degradation effect of PFOA by Pt-EO system was significant. Characterization of the Pt anode, the detection and addition of dissolved platinum ions, and the comparison of Pt with DSA anodes determined that the Pt- ligand complexes resulting from the specific binding of anodically dissolved PtII with ligand ions and C7F15COO- ((C7F15-COO)PtII-L3, L = SCN-, Cl- and N3-) on the electrode surface played a decisive role in the degradation of PFOA. Density functional theory (DFT) calculations showed that inside (C7F15-COO)PtII-L3 complexes, the electron density of the perfluorocarbon chain (including the F atom) compensated toward the carboxyl group and electrons in the PFOA ion transferred to the PtII-Cl3. Moreover, the (C7F15-COO)PtII-Cl3, as a whole, was calculated to migrate electrons toward the Pt anode, leading to the formation of PFOA radical (C7F15-COO•). Finally, with the detection of a series of short chain homologues, the CF2-unzipping degradation pathway of PFOA was proposed. The newly developed Pt-EO system is not affected by water quality conditions and can directly degrade alcohol eluent of PFOA, which has great potential for treating industrial wastewater contaminated with PFOA.

The Difference Of PT, aPTT, Fibrinogen, D-Dimer Activities In HIV Patients With CD4 Count Of <200 uL And >200 uL

ABSTRACT
 Introduction: HIV is a developing disease that has been a global problem. The progress of HIV infection is characterized by decreased CD4 count. Hemostasis disorder is often found in patients with HIV, where the formed virus-antibody complex can activate the coagulation system, beginning from the activation of the Hageman factor (Factor XII) into the active form (Factor XIIa). This factor will activate the fibrinolysis process. Fibrin polymer is broken down into fragments X and Y. Fragment Y is further broken down into Fragment D and E, which is known as D-dimer.
 Objective: To determine the difference of PT, aPTT, Fibrinogen, and D-Dimer in HIV patients with a CD4 lymphocyte count of < 200/µL and > 200/µL in H. Adam Malik General Hospital Medan.
 Hypothesis: There is a difference of PT and aPTT activities in HIV patients with a CD4 count of < 200 cells/µL and ≥ 200 cells/µL and a difference of D-dimer and fibrinogen levels in HIV patients with a CD4 count of < 200/µL and > 200/µL in H. Adam Malik General Hospital Medan.
 Methods: This study was conducted in the Clinical Pathology Laboratory, Department of Internal Medicine, H. Adam Malik General Hospital. Samples were collected with a consecutive sampling method which included patients diagnosed with HIV in H. Adam Malik General Hospital Medan from September 2019 to July 2020 who fulfilled the inclusion and exclusion criteria. Thirty-eight patients were divided into two groups, i.e., HIV patients with a CD4 count of < 200/µL and HIV patients with a CD4 lymphocyte count of > 200/ µL.
 Results: Mann-Whitney test was used to assess the comparison of PT and aPTT values between HIV patients with a CD4 count of < 200 cells/µL and ≥ 200 cells/µL. The result was significant with a p-value = 0.002, which means that there is a significant difference in PT and aPTT values between HIV patients with a CD4 count of < 200 cells/µL and ≥ 200 cells/µL. An Independent T-test was used to assess the difference in fibrinogen level between HIV patients with a CD4 count of < 200/µL and > 200/µL, which resulted in p-value = 0.032. This means that there is a significant difference in fibrinogen levels between HIV patients with a CD4 count of < 200/µL and > 200/µL. Mann-Whitney test was used to determine the comparison in D-dimer level between HIV patients with a CD4 count of < 200/µL and > 200/µL, which showed a p-value = 0.002. This indicated a significant difference in D-dimer level between HIV patients with a CD4 count of < 200/µL and > 200/µL.
 Conclusion: The lower the CD4 lymphocyte count, the higher the activities of PT, aPTT, fibrinogen, and D-dimer in HIV patients.
 
 Keywords: HIV, PT, aPTT, D-Dimer, Fibrinogen, Hemostasis

Comparison of Pt and Pd anode catalysts supported on nanocrystalline Ru–SnO2 for ethanol oxidation in fuel cell applications

The article presents promising catalysts, applicable for direct alcohol fuel cells (DAFC) for portable and mobile applications. The goal of this work is development of Pt and Pd catalysts deposited on interactive nanocrystalline Ru doped SnO2 support with improved performance. The structure and the morphology of the prepared metal-oxide catalyst support and Pt and Pd based catalysts were examined using XRPD, SEM/EDX and TEM techniques. Electrocatalytic activities of the prepared Pt or Pd based catalysts were evaluated in both alkaline and acidic conditions. The ethanol oxidation reaction (EOR) was studied using conventional electrochemical techniques. The interactive nature of the novel Ru doped SnO2 catalyst support was confirmed, resulting in the enhancement of the EOR kinetics, in comparison to commercially available catalysts. New and simplified synthetic route applied for preparation of interactive catalyst support was presented with the aim to enable easy scale-up of the catalyst production process. Obtained results on the novel catalysts promise great potential in improving the performance and durability of the DAFC.

Selective Extraction of Platinum(IV) from the Simulated Secondary Resources Using Simple Secondary Amide and Urea Extractants

The recycling of rare metals such as platinum (Pt) from secondary resources, such as waste electronic and electrical equipment and automotive catalysts, is an urgent global issue. In this study, simple secondary amides and urea, N-(2-ethylhexyl)acetamide, N-(2-ethylhexyl)octanamide, and 1-butyl-3-(2-ethylhexyl)urea, which selectively extract Pt(IV) from a simulated effluent containing numerous metal ions, such as in an actual hydrometallurgical process, were synthesized and achieved efficient Pt(IV) stripping using only water. Comparison of Pt(IV) extraction behavior with a tertiary amide without N–H moieties suggests that the secondary amides and urea extractants effectively use hydrogen bonding to the hexachloroplatinate anion by N–H moieties. Examining the conditions for the third phase formation revealed that the secondary amide extractant with the longest alkyl chain can be used in the extraction process for a long time without forming any third phase, despite its lower Pt(IV) extraction capacity. The practical trial with simple compounds developed in this study should contribute to the development of Pt separation and purification processes.

Comparison of Pt and IrO2-Ta2O5/Ti as a counter electrode in acidic media

Platinum has been widely employed as a counter electrode (CE) for various electrochemical measurements; however, the potential dissolution of Pt from the CE during electrochemical processes may skew the results of electrochemical studies, particularly for cathodic reactions (e.g., hydrogen evolution, oxygen reduction, and CO2 reduction). For this study, we compared the electrochemical behaviors of Pt and IrO2-Ta2O5/Ti electrodes as CEs in 0.5 M H2SO4. To study the effects of various surface areas, a smooth glassy carbon electrode with a small geometric surface area (GSA) of 0.07 cm2 (GCE-s), a smooth medium GCE with a GSA of 0.38 cm2 (GCE-m), and carbon cloth (CC) with a large GSA of 2.00 cm2 were employed as working electrodes (WEs). When Pt was used as the CE, the current of the GCE-s was slowly enhanced after 1000 cycles, while a notable current increase at the GCE-m was seen after 800 cycles. For the CC electrode, a prominent increase in the current was observed after 400 cycles. The increased HER activity was initiated through the deposition of Pt dissolved from the CE during cyclic voltammetric cycles in the potential range between −0.40 and 0.0 V vs. Ag/AgCl. In contrast, no notable current increase was observed for any of the GCE-s, GCE-m, and CC electrodes during 2000 cycles when the IrO2-Ta2O5/Ti electrode was employed as the CE.

Study of coagulation profile in malaria

Background: Malaria is a major health problem in many parts of India. Several factors have beenattributed to increased morbidity and mortality in malaria with altered hematological andcoagulation parameters. This study was conducted to compare the coagulation parameters ofmalaria cases with those of the healthy carriers. Aims and objectives: To evaluate coagulationabnormalities in patients of malaria and to study the difference in coagulation parameters betweenmalaria patients and healthy controls and to determine the level of significance of the difference.Materials and methodology: This prospective comparative study of 300 patients with laboratorydiagnosed malaria patients (cases) and 300 healthy individuals (controls) was carried out in theDepartment of Pathology in a tertiary care, V. S. General Hospital, Ahmedabad. Result: Comparisonof platelet count, PT, and aPTT between case groups and control groups was statistically significant(p<0.001). Conclusion: There is a significant difference between the platelet count, PT, and aPTTvalues of the two groups. This indicates that in patients with malaria, there is an activation ofintrinsic and extrinsic pathways of coagulation.

Platinum and palladium complexes of tridentate −C^N^N (phen-ide)-pyridine-thiazol ligands – A case study involving spectroelectrochemistry, photoluminescence spectroscopy and TD-DFT calculations

Four Pd(II) and Pt(II) complexes [M(C^N^N)Cl] (HC^N^N = 2-(6-phenylpyridin-2-yl)thiazoles) were synthesised, analysed and characterised using 1H NMR and MS in solution, as well as single crystal XRD in the solid. Cyclic voltammetry of the square planar complexes showed reversible or partially reversible reductions and irreversible oxidations. DFT calculations allowed assigning them to essentially metal-centred oxidations and ligand-centred reductions. Absorption spectra of the complexes show intense absorption bands into π-π* states in the UV to visible spectral range and long-wavelength bands which were assigned to transitions into mixed metal-to-ligand charge transfer (MLCT)/π-π* states, based on TD-DFT calculations. Comparison of Pt and Pd derivatives showed that the energy of the (MLCT)/π-π* bands are increased for Pd over Pt. This was also observed for the phosphorescence at 77 K and is attributed to the higher oxidation potential for Pd and supported by spectroelectrochemical measurements. The photoluminescence quantum yield (ΦL) drops drastically from Pt to Pd at room temperature, where only the two Pt(II) complexes are luminescent showing a broad unstructured phosphorescence from a 3MLCT state. At 77 K, the phosphorescence is blue-shifted and shows a clear vibrational progression, which is related to an enhanced ligand-centred character due to the lack of solvent stabilisation in the frozen matrix that otherwise increases the MLCT contribution. The Pd(II) complexes are not emissive at 298 K, but luminesce at 77 K. This is due to metal-centred dissociative d-d* states that facilitate radiationless deactivation, which cannot be thermally populated at low temperatures. Thus, similar ΦL are observed in frozen glassy matrices for both metals. TD-DFT calculations provided insight into the excited states and showed that the substitution pattern does not affect the emission, due to the lack of participation of the phenyl unit in the orbitals that are relevant for the description of the emissive state.

DFT and microkinetic comparison of Pt, Pd and Rh-catalyzed ammonia oxidation

Ammonia oxidation is the heart of the Ostwald process and is important in emissions control. Catalytic behaviors are a function of conditions and are observed to vary across the platinum group metals (PGMs) Pt, Pd, Rh. Here, we combine density functional theory computations and microkinetic modeling to rationalize these dependencies. We compute reactions over model (2 1 1) and (1 1 1) surfaces of PGMs. Binding energies are similar on Pd and Pt and generally greater on Rh, while activation energies vary across all metals. Rates on (2 1 1) surfaces are greater than (1 1 1) surfaces. The stepped Pt is most active and stepped Rh most selective to N2 at ammonia slip conditions, while at Ostwald process conditions, stepped Pd is most active and stepped Pt most selective to NO. Degree of rate and selectivity control analysis provides insights into the reactions limiting performance of PGMs. Both activation barriers and surface coverages influence rates and selectivities.

Stability Comparison of Pt and Ni as Base Metal Catalysts in Anion Exchange Membrane Fuel Cells

Interest in anionic exchange membrane fuel cell (AEMFC) technology has increased in recent years because of the possibility of using a variety of new catalyst materials in the alkaline environment. Pt and Ni are popular base metal substrates for the development of highly active catalysts in many studies. However, for commercial use, catalyst stability is paramount. In commercial applications, such as back-up power systems, catalysts must tolerate high steady state potentials for extended periods of time. This could be detrimental to catalyst materials, especially at the cathode. Yet, the stability of Pt and Ni in AEMFC environment is not fully understood under steady state potential. In this paper, the stabilities of Pt and Ni supported on carbon have been tested using a standby cell potential of 0.9 V, within an AEMFC environment. The study, combined with SEM, TEM, ICP-AES, and ICP-MS analysis results, shows significant morphology changes in the supported Pt and Ni catalyst particles, as well asdissolved Pt and Ni in the AEM electrolyte with 0.14mgPt gAEM−1 and 0.2mgNi gAEM−1 after an one month test period. The Pt migration appears to be driven by the electric field while Ni appears to show generic chemical diffusion.

Comparison of Pt–Cu/C with Benchmark Pt–Co/C: Metal Dissolution and Their Surface Interactions

Understanding of less-noble-metal (M) dissolution from Pt-alloy-based oxygen reduction reaction (ORR) electrocatalysts, as well its interaction with Pt surface, is crucial for maximizing their performance. In pursuing this goal, two ORR electrocatalysts—a benchmark Pt–Co/C and an in-house designed Pt–Cu/C materials—are investigated. Both are characterized with a range of standard techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDX) and thin film-rotating disc electrode (TF-RDE) measurements. A special focus is put on combining the latter with a highly sensitive electrochemical flow cell (EFC) online connected to inductively coupled plasma mass spectrometry (ICP-MS) measurements. A combination of standard and novel techniques provides unprecedented insights into the dissolution behavior and dynamics of metals, as well as their subsequent surface interactions and effects on the electrochemical performance. A special focus is d...

Comparison of Pt and Ag as co-catalyst on g-C3N4 for improving photocatalytic activity: Experimental and DFT studies

Comparison of Pt and Ag as co-catalyst on g-C3N4 for improving photocatalytic activity: Experimental and DFT studies

Cover Image, Volume 92, Issue 9

The cover image, by José Antonio Díaz et al., is based on the Research Article Kinetic modelling of the glycerol oxidation in the liquid phase: comparison of Pt, Au and Ag AS active phases, DOI: 10.1002/jctb.5296. Photo Credit: CNRS Photothèque / Cyril FRESILLON. image

Effect of Pt doping on activity and stability of Ni/MgAl2O4 catalyst for steam reforming of methane at ambient and high pressure condition

Effect of addition of Pt noble metal to Ni/MgAl2O4 catalyst for steam reforming of methane was studied at atmospheric pressure and at high pressure (10 bar). Pt loading of the catalyst was varied from 0.01 wt.% to 1.0 wt.%. Catalyst characterization studies showed that the degree of reduction of the catalyst increased from 44.9% for Ni/MgAl2O4 to 67.7% for the catalyst doped with 1.0 wt.% Pt, which was attributed to H2 spill over effect. With increasing Pt loading, the metal dispersion passed through a maxima and the highest dispersion of active metals was obtained with a Pt doping of 0.1 wt.%. Increase in Pt concentration had no effect on the concentration of NiAl2O4 that had already formed during calcination at 850 °C after nickel impregnation. Addition of Pt significantly increased the catalytic activity of Ni/MgAl2O4 for the steam reforming of methane at both reactor pressures. Comparison of Pt doped Ni/MgAl2O4 with Pt/MgAl2O4 showed that only lower loading of Pt produced a synergetic effect. The highest catalytic activity was obtained with 0.1 wt.% Pt doped Ni/MgAl2O4. Above this Pt loading the catalytic activity decreased. The highest activity of 0.1 wt.% Pt doped catalyst was credited to an increase in active metal dispersion, while the decrease in catalytic activity on further addition of Pt was attributed to agglomeration of active metals. High pressures decreased the conversion and stability of each Pt doped catalyst. However, at the same operating conditions there was a marginal increase in the catalyst stability due to Pt doping and the decline in catalyst activity with run time was lowest for 0.1 wt.% Pt doped Ni/MgAl2O4 catalyst.

Kinetic modelling of the glycerol oxidation in the liquid phase: comparison of Pt, Au and Ag AS active phases

AbstractBACKGROUNDUnlike Pt and Au, Ag has recently been reported to be an active catalyst for the synthesis of glycolic acid from the liquid phase oxidation of glycerol (GLY). In order to provide comparative information about the kinetics of this reaction using Pt, Au or Ag, a kinetic model was derived for each catalyst (Ag/, Pt/ and Au/Al2O3), using the experimental results obtained at different temperatures.RESULTSA power‐law kinetic model was proposed for each catalyst, which included the Khang–Levenspiel model to evaluate potential catalyst deactivation. All three kinetic models predicted well the experimental concentrations. Pt/ and Au/Al2O3 showed higher kinetic rate constants, the highest being that of the production of glyceric acid. The lower the metal particle size, the higher the kinetic rate constant of the production of glyceric acid was. Deactivation parameters played an important role in the model of Pt/Al2O3, so that Au/ and Ag/Al2O3 seemed to be more resistant to deactivation.CONCLUSIONSThis work reports the first kinetic model for the oxidation of GLY using an Ag‐based catalyst. It showed a noticeable kinetic rate constant for the production of glycolic acid. The activation energies obtained were in the range 48–97 kJ mol−1. © 2017 Society of Chemical Industry

A Comparison of Pt(II) and Pt(IV) Chloride Precursors for Strong Electrostatic Adsorption Synthesis of Pt/Alumina and Pt/Carbon Catalysts

Platinum (II) tetrachloride (PTC) has been studied as an anionic metal precursor in strong electrostatic adsorption method of catalyst preparation. Compared to the conventionally used platinum (IV) hexachloride precursors, PTC exhibited greater pH stability in aqueous solution. As a result, PTC uptake on high PZC supports remained nearly unchanged irrespective of precursor aging. Upon reduction of these PTC catalysts small (~2.0 nm) and well-dispersed Pt nanoparticles were obtained on alumina, whereas on carbon, Pt sizes were significantly larger (4–10 nm).

Catalytic regeneration of Diesel Particulate Filters: Comparison of Pt and CePr active phases

Diesel Particulate Filters (DPFs) have been loaded with the same amount (0.6wt.%) of either Pt or an optimized CePr active phase, and an experimental set-up has been designated and used to investigate the catalytic combustion of soot under realistic reaction conditions. Both active phases were stable under reaction conditions, with no evidences of deactivation in consecutive combustion experiments. The presence of H2O and CO2 together with NOx and O2 in the gas mixture slightly delays soot combustion to higher temperatures, but the effect is equal for the Pt and CePr active phases. The mass of soot loaded into the filters had no effect in the catalytic regeneration of the DPFs for soot:catalyst weigh ratios below 0.4, while it was hindered above this ratio. The Pt and CePr active phases behave equal until 0.6 soot:catalyst weigh ratio and Pt performance was slightly better for higher soot loading. This difference is explaining according to the main soot combustion mechanisms occurring during Pt–DPF (NO2-assited) and CePr–DPF regeneration (active oxygen). The CO2 selectivity is near 100% for both catalysts in all the experimental reaction conditions evaluated. According to this study, the CePr active phase seems to be a promising candidate to replace Pt in real applications.

Comparison of Pt and Pd Modified TiO2 Gas Sensors

Pt and Pd have been widely used to improve response properties of TiO2 based gas sensors. In this work, differences on response properties, especially the response time of Pt/TiO2 and Pd/TiO2 sensors, were carefully compared. TiO2 sensing films were modified by dipping method using H2PtCl6 and PdCl2, respectively. XRD, XPS and SEM were used to characterize the crystal structure, elemental composition and grain size of the sensing films. The defect state was characterized by the relationship between resistance and oxygen partial pressure. And the response transients to H2 and O2 were tested by voltammetry method. The difference on response properties of modified TiO2 sensors were suggested to arise from their activation energy. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6403

Platinum–Rhenium Synergy on Reducible Oxide Supports in Aqueous‐Phase Glycerol Reforming

AbstractA significant support effect was observed for the aqueous‐phase reforming (APR) of glycerol over a series of Pt‐ and PtRe‐loaded ceria‐, ceria–zirconia‐, zirconia‐, and titania‐supported catalysts. Glycerol conversion rates decreased in the order Pt/TiO2>Pt/ZrO2>Pt/CeZrO2>Pt/CeO2. Upon addition of Re, APR activities of all the Pt catalysts increased. Re promotion for glycerol APR was strongest for PtRe/CeO2. Pt/CeO2 was least active because of the incomplete reduction of Pt. Pt was more easily reduced in PtRe/CeO2 because of the strong Pt–Re interaction. On comparison with previous data on Pt/C and PtRe/C, the oxide‐supported catalysts were more active in the WGS reaction, with the titania‐supported catalyst as the most active, which was a result of the activation of water on the titania support. The acidity of these groups also resulted in increased CO cleavage rates of Pt/TiO2 relative to the rates of Pt/C in APR. A more detailed comparison of Pt(Re)/C and Pt(Re)/TiO2 is made. Monitoring acetaldehyde decomposition to determine the rate of CC bond cleavage evidenced a strong promoting effect of Re on the supported Pt catalysts. All catalysts produced carbon monoxide, methane, and ethanol during acetaldehyde decomposition; notably, Pt(Re)/TiO2 also formed products such as ethylene, ethane, propylene, and propane, indicative of a mechanism also involving ethanol dehydration and olefin coupling to CHx surface intermediates derived from acetaldehyde. The activity in overall glycerol conversion in APR decreased in the order PtRe/C>PtRe/TiO2>Pt/TiO2>Pt/C.