Effect Of Pt Addition Research Articles

Synergistic effects of Pt and Y addition in (Ni, Pt)CrAlY bond coat on oxide spallation resistance and growth of interdiffusion zone between bond coat and Ni-based single crystal superalloy

This study shows the beneficial effect of Pt addition to the (β+γ)-NiCrAlY coating. Adding Y in NiCrAl increases oxide growth kinetics but improves spallation resistance. Pt with Y does not change the oxidation rate compared to only adding Y but significantly reduces spallation when cooled to room temperature. Continuous layers of Al2O3 and Cr2O3, along with other oxides such as YAlO3, NiCr2O4, and NiAl2O4, are observed. Moreover, Pt addition reduces the thickness of the interdiffusion zone where Al goes through an uphill diffusion profile, minimizing Al loss and significantly decreasing the growth of deleterious TCP phases.

Unveiling the effect of Pt addition on Ag/C catalyst for enhanced glycerol electrooxidation

This study investigates the performance of Ag/C and a range of Ag100-xPtx/C nanoparticles as electrocatalysts for glycerol electrooxidation reaction (GEOR). Low amounts of Pt (<2 %) were spontaneously deposited on Ag-supported nanoparticles using Ag as a sacrificial metal. The primary aim of the study is to determine the impact of adding a small amount of Pt to the Ag/C catalyst. Cyclic voltammetry is employed to assess the electrocatalyst's performance, while in situ Fourier Transform Infrared (FTIR) spectroscopy is used to examine the formed reaction intermediates and products. Additionally, physical characterization techniques such as XRD and XPS are applied to analyze the material structure. The Ag100-xPtx/C series of catalysts show a significant improvement in the glycerol oxidation process with the addition of 0.25 % of Pt to the material composition compared to pure Ag. It is observed that the enhancement performance reaches a limit at a Pt composition of approximately 7 % in the metallic nanoparticles, indicating that further increases in Pt content do not yield additional improvements. The in situ FTIR studies reveal that the presence of Pt on the Ag surface leads to a distinct glycerol electrooxidation mechanism compared to using Ag alone. Small amounts of Pt deposits promote C−C−C bond breaking, as evidenced by the selective formation of formic acid and CO2. FTIR results demonstrate a preference for carboxylic acid formation, with no significant evidence of dihydroxyacetone (DHA) production. The findings emphasize the critical role of Pt composition in the electrooxidation of glycerol paving the way for the design and development of more efficient and sustainable electrooxidation catalysts.

Effect of Pt Addition on the Oxidation and Corrosion Resistance of Al0.25CoCrFeNi High-Entropy Alloy

The effect of minor platinum alloying on the microstructure, phase composition, oxidation and corrosion resistance of Al0.25CoCrFeNi high-entropy alloy (HEA) has been studied. It was observed that Pt does not segregate as a separate phase, but it is incorporated into the fcc solid solution. High-temperature oxidation of the as-cast Al0.25CoCrFeNi and Al0.25CoCrFeNiPt0.1 high-entropy alloys was carried out in a muffle furnace under isothermal conditions at 900 °C for 0–50 h (weighing was carried out every 10 h) in air atmosphere. The specific weight gain decreased from 0.58 mg/cm2 for Al0.25CoCrFeNi to 0.31 mg/cm2 for the platinum-doped Al0.25CoCrFeNiPt0.1 sample. It was determined that Pt triggers the formation of an interlayer Al-rich oxide phase between the outer Cr-rich oxide layer and the interior of the alloy, significantly reducing the oxidation rate of Al0.25CoCrFeNiPt0.1 HEA. Electrochemical tests in 0.5 M H2SO4 solution demonstrated passive behavior with anodic control of the process.

Highly dispersed Pt boosts active FexN formation in ammonia decomposition

Ammonia decomposition plays an important role in hydrogen production, especially in the context of a hydrogen economy. Fe-based catalysts are a popular choice due to their affordability and moderate activity, making them attractive for large-scale applications. However, the transformation of Fe-based catalysts into more active FexN species can be slow, resulting in a prolonged induction period. To address this issue, we investigated the effects of Pt addition on FexN formation in ammonia decomposition. Our results show that even a slight Pt addition significantly enhances the FexN formation rate, increasing it over threefold. Pt aids in H2 desorption via reverse spillover, which, in turn, exposes more Fe surface sites where nitridation occurs, leading to the formation of iron nitride. Characterization via High-angle annular dark-field imaging scanning transmission electron microscopy, X-ray diffraction, and in situ X-ray absorption spectroscopy (XAS) revealed the formation of Fe2N as active species, whereas temperature-programmed hydrogen desorption, temperature-programmed reduction by hydrogen, and in situ XAS supported the existence of H reverse spillover and spillover effects. Overall, our study provides an improved understanding of the active species formation mechanism of Fe catalysts in ammonia decomposition and offers a simple strategy for improving their catalytic performance.

Effect of Pt Addition on the Formation of Ni–Pt Porous Layer

A Ni–Pt alloy porous layer was formed by electrodepositing Pt using Ni as the substrate sample, followed by Al-depositing and Al-dissolving. The Pt was electrolyzed using an aqueous solution as the medium, and the Al-depositing and Al-dissolving were treated using a molten salt as the medium. The molten salt used was NaCl–KCl with 3.5 mol% AlF3 added. It was found that Pt electrodeposition formed on the surface had a finer structure. Furthermore, it was clarified that the lower the electrodeposition potential, the thicker the Ni-Pt alloy porous layer. The cathode polarization curve was measured in KOH solution, and the hydrogen gas was determined when a constant voltage electrolysis was performed with a hydrogen detection gas sensor using a tubular yttria-stabilized zirconia (8 mol% Y2O3–ZrO2).

Exploring the Effect of Pt Addition on the Fracture Behavior of CrN Coatings by Finite Element Simulation

Previous research confirmed that Pt addition induced a prominent refinement effect of CrN coating, resulting in an enhanced conductivity and corrosion resistance. In this work, a detailed finite element simulation and scratch test were employed to calculate and characterize the fracture failure behaviors (stress distribution, crack damage process, critical coating load, and coating–substrate adhesion energy) of CrN coatings with different Pt contents. Simulation results showed that the synergistic action of dynamic scratch load and extrusion load induced the fracture of the coatings. S11 and S22 caused transverse cracks in the CrN coating, S11 caused longitudinal cracks in the CrN-Pt coating and CrN-3Pt coatings, S22 led to the inclined propagation of cracks in these coatings, and S11 and S22 jointly induced the separation of the coating from the substrate. The doping Pt element in the CrN coating will make the coating easier to fracture and reduce the adhesion strength between the coating and substrate. Scratch test results revealed that adding Pt into the CrN coating will make this coating easier to fracture and cause more serious damage; the simulation results are in good accordance with the scratch test characterizations. The current founding provided a comprehensive understanding for the fracture damage mechanism of Pt-doped nitride coatings.

Catalytic synthesis of segmented carbon filaments via decomposition of chlorinated hydrocarbons on Ni-Pt alloys

Abstract A series of micro-disperse Ni1-xPtx alloys with the sponge-like structure was prepared by a simultaneous precipitation method with subsequent sintering of the sediment in H2 atmosphere at 800 °C. The formation of single-phase solid solution Ni1-xPtx was confirmed by powder XRD analysis for entire range of Pt concentrations (1.3–75.9 wt.%). The synthesized samples were studied in a process of catalytic decomposition of C2H4Cl2 at 600 °C. In situ kinetic studies of the carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. Interaction of Ni-Pt alloys with reaction mixture is characterized by an induction period (18–32 min) followed by rapid disintegration of the bulk alloys with intensive growth of carbon fibers. The stage of the induction period was explored in detail by means of XRD and SEM techniques. According to XRD data, the interaction of Ni-Pt alloys with C2H4Cl2 vapors is accompanied by formation of Ni1-xPtxCδ interstitial solution due to entry of carbon into the crystal lattice of the alloy. The effect of Pt addition on catalytic activity of Ni in CCVD process was also studied. It was found that the yield of carbon product depends extremely on Pt concentration with a maximum at CPt =4.3 wt.% (26 g/gNi for 120 min). The impact of Pt concentration upon morphology and structural features of the produced carbon fibers was investigated by SEM and TEM techniques.

The Direct Synthesis of H2O2 Using TS‐1 Supported Catalysts

AbstractIn this study we show that using AuPd nanoparticles supported on a commercial titanium silicate (TS‐1) prepared using a wet co‐impregnation method it is possible to produce hydrogen peroxide from molecular H2 and O2 via the direct synthesis reaction. The effect of Au: Pd ratio and calcination temperature is evaluated as well as the role of Pt addition to the AuPd supported catalysts. The effect of Pt addition to AuPt nanoparticles is observed to result in a significant improvement in catalytic activity and selectivity to hydrogen peroxide with detailed characterisation indicating this is a result of selectively tuning the ratio of Pd oxidation states.

Magnetic Properties of FeCoWYB-based Ferromagnetic Alloys with a Small Addition of Pt

The paper presents the results of research on the effect of Pt addition in the amount of 2 to 3% at. in to bulk Fe61Co10B20Y8-xW1Ptx alloy on its structure and magnetic properties. Alloys in the form of tiles were made by pressing a liquid alloy into a copper liquid-cooled mold. Structural examinations were carried out using X-ray diffraction (XRD). The magnetic properties were examined using a vibration magnetometer (VSM). Based on structural investigations, the occurrence of crystalline phases, i.e.: a-Fe, Fe2B, FePt, Fe3Pt, FePt3, was found. The results of VSM tests showed that both saturation magnetization (m0Ms) and coercive field (Hc) significantly increased. The study showed that even a small change in the Pt content in the alloy affects its structure and thus significantly affects the magnetic properties.

Effect of Pt addition on resistance to carbon formation of Ni catalysts in methane dehydrogenation over Ni-Pt bimetallic surfaces: A density functional theory study

Methane dehydrogenation is a well-studied reaction that is of both scientific and industrial importance. We performed systematic density functional theory computations to examine the catalytic performance of pure and Pt modified Ni(111) surfaces for carbon formation from methane dehydrogenation. To address these processes, Ni-Pt surface alloys of 6 different bimetallic compositions are applied to investigate the detailed catalytic dehydrogenation for methane, and their catalytic activities as well as resistance to carbon formation are compared with monometallic Ni(111) surface. Through the systematic examination, the results show that CH4 dissociation into CH3+H and CH decomposition into C+H are the two key steps. Moreover, it is found that CH dissociation barriers on the Ni-Pt bimetallic surfaces are evidently higher that on pure Ni(111). Especially for NiPt(111)-B1 surface, energy barrier for CH dissociation is remarkably increased by around 1.7eV compared to that on Ni(111) and the carbon adsorption energy is the lowest one among all surfaces. The enhanced barrier suppresses the CH cracking reaction and reduced carbon adsorption energy diminishes the possibility of coke formation. Additionally, carbon formation is significantly inhibited even with a small amount of Pt addition. Considering the balance between the catalytic performance and the economic cost, we proposed that NiPt(111)-B1 surface not only exhibits good resistance to carbon formation, but also has the moderate cost due to the less doped Pt atoms, although there is a slight decrease in activation for methane. Finally, BEP relationships between reaction energy and activation energy have been developed for every methane dehydrogenation step on all Ni(111) and NiPt(111) surfaces in this paper. These results could provide new mechanistic insight into the role of Pt in improving the ability to anti carbon formation of Ni catalysts, and are helpful to understand the mechanisms of methane dissociation from the atomic scale.

Effect of Pt addition on sulfur dioxide and water vapor tolerance of Pd-Mn-hexaaluminate catalysts for high-temperature oxidation of methane

An effect of Pt addition to improve the catalytic performance of Pd-modified Mn-hexaaluminate in the high-temperature oxidation of methane, especially in SO2 and water presence, has been studied. X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and differential thermal analysis were used for the characterization of fresh and spent catalysts. Temperature-programmed reduction by hydrogen was employed to study the redox properties of the catalysts. Four high-temperature tests (at 670°C) of the methane oxidation were applied to reveal the water and sulfur resistance of the catalysts: 1) dry methane-air feed; 2) wet methane-air feed containing 3wt% of water vapor; 3) methane-air feed containing 1000ppm of SO2; and 4) wet methane-air feed with 1000ppm of SO2. The Pt-doped Pd-Mn-hexaaluminate catalyst with the atomic ratio of Pt/Pd<0.3 has been shown to possess the highest catalytic activity in the oxidation of methane, high water and sulfur tolerance, and reducibility by hydrogen as compared to the monometallic Pd-Mn-hexaaluminate catalyst and the bimetallic catalysts with Pt/Pd>0.5. From the formal kinetic data of the oxidation of methane on the fresh and deactivated catalysts, we assumed that deactivation of the catalysts is due to a decrease in the amount of catalytically active sites in the bimetallic 0.33Pt-0.67Pd(0.27)/MnLaAl11O19 catalyst and a change in the state of active component in the other catalysts. Their oxidation ability and redox behavior were shown to be associated with the highly dispersed PdO particles, a PdO layer (3–5nm) covering the metal palladium particles as well as the Mn3+-enriched MnLaAl11O19. The improved water and sulfur resistance is found to correlate with the presence of particles of PtPd alloy, with its fraction not exceeding 50%.

Structure and properties of Pd–Mn hexaaluminate catalysts modified with platinum for the high-temperature oxidation of methane

The effect of Pt additives on the catalytic characteristics of a Pd-containing catalyst based on manganese hexaaluminate was studied. It was found that the bimetallic PtPd-containing catalysts based on MnLaAl11O19 with the Pt/Pd atomic ratio smaller than 0.25 exhibited a comparable or somewhat smaller activity in the methane oxidation, but their stability at elevated temperatures and gas flow rates was higher than that of the Pd-based catalyst. The state of the active constituent of the resulting catalysts was investigated. Main correlations between the state of the active component and the catalytic activity were revealed.

Ethanol conversion at low temperature over CeO2—Supported Ni-based catalysts. Effect of Pt addition to Ni catalyst

The effect of Pt addition on the performance of Ni/CeO2 catalyst for the low temperature steam reforming of ethanol is investigated. The reaction mechanism was explored using diffuse reflectance infrared spectroscopy under reaction conditions and temperature-programmed surface reaction of ethanol. The addition of Pt to Ni/CeO2 catalyst promoted the decomposition of dehydrogenated and acetate species to hydrogen, methane, CO and carbonate species. Furthermore, the presence of Pt reduced the rate of catalyst deactivation. In situ X-ray absorption studies revealed the formation of a nickel carbide phase during steam reforming of ethanol over Ni/CeO2 catalyst, which was associated with amorphous carbon deposition and catalyst deactivation. X-ray photoelectron spectroscopy in combination with kinetic and structural data was consistent with a partial Pt monolayer on Ni in the bimetallic catalyst. The segregation of Pt on the surface of the Ni particles minimized the formation of nickel carbide and promoted catalyst stability.

BiFeO3–CoFe2O4–PbTiO3 composites: structural, multiferroic, and optical characteristics

Three-phase magnetoelectric composites (1 - x) (0.7BiFeO3-0.3CoFe2O4)-xPbTiO3 (or equivalently written as (1 - x)(0.7BFO-0.3CFO)-xPT) with x variations 0, 0.30, 0.35, 0.40, 0.45, and 1.0 were synthesized using hybrid pro- cessing route. The effects of PT addition on structural, mul- tiferroic, and optical properties have been subsequently investigated. A detailed Rietveld refinement analysis of X-ray diffraction patterns has been performed, which confirms the presence of structural phases of individual constituents in the composites. Field emission scanning electron microscopy images are taken for microstructural analysis and grain size determination. Transmission electron microscopy analysis of 0.3CFO-0.7BFO reveals the average particle size to be lying in the window of 10-15 nm. The temperature-dependent dielectric constant at various frequencies (1, 10, 50, 100, and 500 kHz) has been studied, and the dielectric study reveals the increase of dielectric constant and decrease of average dielectric loss of composites with incorporation of PT content. Room temperature ferromagnetic behavior of composites is confirmed through the observation of magnetization versus magnetic field (M-H) hysteresis loops. The variation of magnetization with temperature indicates the presence of spin glass behavior in composites. Magnetoelectric coupling is evidenced in the composites through the observation of dependence of the dielectric constant on magnetic field, and magnetodielectric response of 2.05 % is observed for 45 mol% addition of PT content. The fractional change of magnetic field-induced dielectric constant can also be expressed as Der * cM 2 , and the value of c is found to be *1.08 9 10 -2 (emu/g) -2 for composite with x = 0.40. Fourier transformed infrared spectroscopy of samples is car- ried out to analyze various bonds formation in the composites.

High suppression of the formation of ethylbenzene in benzene alkylation with methanol over ZSM-5 catalyst modified by platinum

The generation of ethylbenzene is difficult to be avoided in benzene alkylation with methanol over ZSM-5 catalysts to produce toluene and xylene. Moreover, the separation or removal of ethylbenzene from C8 aromatic yet remains as a major challenge. In this study, the effect of Pt addition on the catalytic performance of ZSM-5 for benzene alkylation was investigated. It was found that the presence of a small amount of Pt in ZSM-5 catalyst would largely suppress the formation of ethylbenzene and extend the life-span of the catalyst, which was mainly due to the hydrogenation of ethylene into ethane on Pt particles.

The effects of Pt addition to supported Ni catalysts on dry (CO2) reforming of methane to syngas

Ni/CeZrO2 and Ni/Al2O3 catalysts promoted by Pt were explored for dry reforming of methane at temperatures ranging from 100°C to 800°C. Temperature programmed reduction (TPR) and temperature programmed reaction studies showed that Pt increases the reducibility of Ni-based monometallic catalysts. TPR studies suggested an alloy formation between Pt and Ni. The induction period with the Pt is much lower than on the Ni alone especially on the Al2O3. At lower temperatures, the Pt–Ni bimetallic catalyst showed slightly higher activity for hydrogen production during dry reforming of methane. Reaction investigations over alumina supported catalysts demonstrated a higher H2:CO ratio than ceria supported catalysts. A mechanism involving more steam reforming due to more water consumption is proposed for the reaction on alumina supported catalysts.

Effect of Pt addition to Ni/La0.7Sr0.3AlO3−δ catalyst on steam reforming of toluene for hydrogen production

Pt/Ni/La0.7Sr0.3AlO3−δ (Pt/Ni/LSAO) catalyst showed high catalytic activity and low coke formation for hydrogen production by steam reforming of toluene, even without pre-reduction. STEM-EDX and XAFS analyses revealed that Pt and Ni formed adjacent or alloy structure. Electron donation from supported Pt to Ni was observed by XPS observation, and the improvement of reducibility of Ni by Pt addition was observed by H2-TPR. Catalytic activity of the reduced Ni was brought by the PtNi interaction. The impregnation order of Pt and Ni affected the catalytic activity and the amount of coke formation due to the difference of the structure of supported metals. Dilution effects of Pt on Ni metal and the contact between Ni and LSAO support apparently affect the suppression of coke formation.

Cyclohexane photocatalytic oxidation on Pt/TiO2 catalysts

Gas-solid heterogeneous photocatalytic oxidation (PCO) of cyclohexane in humidified air over TiO2 and Pt/TiO2 catalyst was studied.Pt/TiO2 photocatalysts were synthesized by photodeposition method at different Pt loadings (0.5–2wt.%). The addition of 0.5wt.% Pt does not significantly modify the TiO2 properties. The increase in Pt loading induces to an aggregation of metallic particles on TiO2 surface.The cyclohexane PCO was performed in a fluidized bed photoreactor at 60 and 100°C. Pure TiO2 was more active than 1 and 2wt.% Pt/TiO2 samples at 60°C. Nevertheless, the conversion level increases with temperature on Pt/TiO2 photocatalysts. The cyclohexane was mineralized into CO2, water and low amount of CO. A beneficial effect of Pt addition was found, since total CO2 selectivity was obtained. The Pt/TiO2 photocatalysts prepared by photodeposition provide the total cyclohexane PCO without CO production. Photocatalysts deactivation was not observed in any performed test. Evidence of an opportune tuning of temperature is highlighted.

Reversible hydrogen desorption from LiBH4 catalyzed by graphene supported Pt nanoparticles

The thermally induced de-/rehydrogenation performance of the graphene supported Pt nanoparticles (Pt/G) doped LiBH4 was greatly improved even at very low catalyst content due to a synergetic effect of Pt addition and nanoconfinement in graphene. For the 5 wt% Pt/G doped LiBH4 sample, the onset hydrogen desorption temperature is about 140 °C lower than that of the pure LiBH4. With increasing loading of the Pt/G catalysts in LiBH4 samples, the onset dehydrogenation temperature and the two main desorption peaks from LiBH4 were found to decrease while the hydrogen release amount increased. About 17.8 wt% can be released from the 50 wt% Pt/G doped LiBH4 sample below 500 °C. Moreover, variation of the equilibrium pressure (350-450 °C) indicates that the dehydrogenation enthalpy is reduced from 74 kJ mol(-1) H2 for the pure LiBH4 to ca. 48 kJ mol(-1) H2 for the 10 wt% Pt/G doped LiBH4, showing improved thermodynamic properties. More importantly, a reversible capacity of ca. 8.1 wt% in the 30th de-/rehydrogenation cycle was achieved under 3 MPa H2 at 400 °C for 10 h, indicating that the Pt/G catalysts play a crucial role in the improvement of the hydrogen uptake reversibility of LiBH4 at lower temperature and pressure conditions. Especially, LiBH4 was reformed and a new product, Li2B10H10, was detected after the rehydrogenation process.

On the phase composition changes during high temperature oxidation of Pt-modified β-NiAl at 1150°C

The phase composition of the scales growing during oxidation at 1150°C on Pt-free and Pt-containing (0, 5, 10 and 15 at.%) β-NiAl intermetallic compounds were studied for exposure periods of up to 6 hours using photoluminescence spectroscopy with spatial resolution down to ca 1 μm. Scanning electron microscopy was used to observe the evolution of the surface morphology of the growing scales. It was found that initially unstable polymorphs of Al2O3 oxide (γ, δ and/or θ) developed, which subsequently transformed into α-Al2O3. The transformation occurred relatively early, and after 1 h oxidation essentially α-Al2O3 was detected on all the materials. After 15 min reaction, different regions were found in all cases, and both types of phases, transient aluminas and α-Al2O3 were detected. However, the rate of the phase composition depended on the region: in some regions, the transient aluminas co-existed with a-phase, while in others only transient or only α-Al2O3 were found. Regions composed of only α-Al2O3 were observed on materials containing higher amounts of Pt-additions, i.e. 10 and 15 at.%. This indicates that Pt additions accelerated the phase transformation of alumina polymorphs into α-Al2O3. In the early scales, comprising different regions, α-Al2O3 development was favoured in patches, and only this phase was always detected in ridges growing in cracks formed in patches. Conclusions are inferred concerning the scale evolution on the materials studied as well as on the effect of Pt additions.