High Dispersion Of Platinum Research Articles

PLATINUM ON REDUCED GRAPHENE OXIDE NANOSHEETS OBTAINED UNDER MICROWAVE IRRADIATION, USING REDUCING AGENTS

Hydrophobic catalysts used in catalytic detritiation process of heavy water consist of platinum impregnated on charcoal (commercial material) and PTFE. For this type of material, Pt is found as agglomerates leading to an increase of hydrophilicity in the final catalyst and also, to a low number of functional groups for isotopic exchange. Therefore, in order to avoid these drawbacks, another type of platinum-based material was considered, with a higher platinum dispersion which would lead to an increase number of functional groups for the isotopic exchange process. There are different methods to synthesize Pt on graphene composites, but using microwaves involves advantages like fewer stages and shorter time to produce. The obtaining method uses reduction of H2PtCl6 in the presence of ethylene glycol and other reducing agents (NaBH4 and KOH) and graphene oxide suspension. Samples were then microstructurally investigated using SEM, BET, X-ray diffraction, RAMAN and TGA.

Highly dispersed platinum deposited on nitrogen-doped vertical graphene array for efficient electrochemical hydrogen evolution

The electrochemical hydrogen evolution is a key technology for future renewable energy conversion and storage. Platinum is the most efficient catalyst for hydrogen evolution reaction (HER), but its mass activity should be boosted further. Herein, we deposited platinum on nitrogen-doped vertical graphene through an atomic layer deposition method. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy confirmed that the platinum was highly dispersed on the array substrate. On account of the array structure and high dispersion of platinum, the synthesized catalyst exhibited high HER performance with a low overpotential of 42 mV at 10 mA cm−2 and a low Tafel slope of 52.2 mV dec−1. Significantly, the synthesized catalyst exhibited a high mass activity of 4.45 A mg−1 Pt, which was ∼13 times higher than that of commercial Pt/C.

Bifunctional catalyst of mordenite‐ and alumina‐supported platinum for isobutane hydroisomerization to n‐butane

Abstractn‐Butane has higher value‐added applications than isobutane in the petrochemical process. To improve the catalytic performance of isobutane isomerization catalysts, catalysts of mordenite‐ and alumina‐supported platinum were prepared. The intimacy between metal and acid sites and platinum content was investigated. The effect of reaction conditions on the catalytic performance of the catalyst was analyzed by response surface methodology. The characterization results of X‐ray diffraction (XRD) patterns, specific surface area, and transmission electron microscope (TEM) confirmed high dispersion of platinum on the catalysts. The results of temperature‐programmed desorption of ammonia (NH3‐TPD) indicated that more acid sites existed on millimetre scale and centimetre scale catalysts than on Pt‐HM/Al2O3 and Pt‐Al2O3/HM, which led to low selectivity of n‐butane. The best yield of n‐butane was attained on microscale samples, as the larger diffusion distance inhibited the cracking reaction. The dispersion of reaction products indicated that the increase of platinum content slightly increased the selectivity of n‐butane. Compared with Pt‐HM/Al2O3, Pt‐Al2O3/HM showed high stability due to fewer carbon deposits in the catalytic reaction process. The optimal reaction condition in isobutane isomerization was T = 413.4°C, liquid hourly space velocity (LHSV) = 5.31 h−1, and P = 2.57 MPa.

Hydrodeoxygenation of guaiacol over Pt-Ga-mesoporous catalysts

The hydrodeoxygenation (HDO) of guaiacol as model compound has been studied in a batch reactor over SBA-15 and Ga-SBA-15 supported platinum catalysts at 12 atm of H2 and different temperatures. Gallium incorporation as heteroatom into the mesoporous siliceous framework modified the nature of the support generating Brønsted acidity. The catalysts were characterized by means of X-ray diffraction, N2 isotherms, XPS, TPR, CO chemisorptions, Py FTIR and TEM. Good structure, narrow pore size distribution and high platinum dispersion were achieved in the synthesized catalysts. The catalysts were very active in the conversion of guaiacol at 200 °C, almost complete conversion was obtained in 3 h of reaction. Mild acidity generated by gallium incorporation enhanced the dispersion of platinum active species and improve the HDO ratio.

Comparative activity and hydrothermal stability of FeOx- and CeO2-doped Pt-based catalysts for eliminating diesel emissions

Diesel emissions (CO/C3H6/ NO) were eliminated on FeOx-doped and CeO2-doped Pt-based catalysts respectively to compare reaction mechanism and performance features. FeOx-doped catalyst has a higher platinum dispersion, a higher platinum valance state retarding CO adsorption and a higher oxygen mobility. Both of the higher dispersion and the oxygen mobility have a positive role in low-temperature catalytic oxidation performance, lower by 26 °C for CO light-off temperature and 12 °C for C3H6 light-off temperature respectively than CeO2-doped catalyst. On FeOx-doped catalyst, the lesser surficial active oxygen species form the byproduct Fe(NO), resulting in an reduction of 10% NO maximum conversion. Besides, hydrothermal aged FeOx-doped catalyst with reduction treatment show a relatively lower light-off temperature and a higher NO max conversion. The difference in reaction characterization enlighten that the composition of oxidation catalyst would focus on the specific performance for the practical configuration in aftertreatment system for the better diesel emissions prevention.

PtNi/C bimetallic nanocatalyst with high catalytic performance and stability for 1-nitronaphthalene hydorgenation to 1-naphthylamine

In this report, the Ni/C sample was successfully prepared at room temperature (RT) by depositing nickel related species on carbon black by a chemical liquid reduction method with hydrazine hydrate as reducing agent, Pt/C was synthesized via a wetness impregnation method. And Pt was supported on Ni/C by galvanic replacement reaction to form PtNi/C bimetallic nanocatalyst. By comparing the catalytic performance of different catalysts for 1-nitronaphthalene hydrogenation, it could be found that the PtNi/C bimetallic nanocatalyst showed higher catalytic activity than monometallic nanocatalysts (Pt/C and Ni/C), exhibiting 100 % conversion of 1-nitronaphthalene, 100 % selectivity to 1-naphthylamine and turnover frequency of 194.9 h−1 under mild reaction conditions (40 min, 30 °C, 3.0 MPa H2). The as-prepared catalysts were characterized by XRD, XPS, HAADF-STEM, STEM-EDX mapping and line-scanning, TG, HRTEM and H2-TPD, which proved that PtNi/C showed most outstanding catalytic behaviors in 1-nitronaphthalene selective hydrogenation due to high dispersion of platinum, the nanostructure of Pt-on-Ni-on-Ni(OH)2 and thus synergism effect among Pt, Ni and Ni(OH)2.

Zinc-modified Pt/SAPO-11 for improving the isomerization selectivity to dibranched alkanes

Zinc-modified Pt/SAPO-11 catalysts were prepared by incipient wetness impregnation and assessed in the hydroisomerization of n-octane. Their physicochemical properties were investigated using powder X-ray diffraction, scanning electron microscopy, nitrogen adsorption-desorption, pyridine-adsorbed infrared spectroscopy, temperature-programmed desorption of NH3, temperature-programmed reduction of hydrogen, temperature-programmed desorption of hydrogen, transmission electron microscopy, and X-ray photoelectron spectroscopy. The addition of zinc resulted in high dispersion of platinum. Zinc acted as a competitive adsorbent, changed the location of platinum. The catalyst with a zinc loading of 0.5% gave the highest selectivity to dimethylhexanes, but the conversion was lower than those achieved with the other catalysts. Dimethylhexanes have large molecular diameters, and therefore their diffusion may be difficult. This weakens the catalytic activity of the zinc-modified catalysts and lowers the n-octane conversion.

Morphological effect of lanthanum-based supports on the catalytic performance of Pt catalysts in crotonaldehyde hydrogenation

Rod-like and particle-like La2O2CO3 and La2O3 were obtained via morphology-preserved thermal transformation of the La(OH)3 precursors. La2O2CO3- and La2O3-supported Pt catalysts were prepared by impregnation method and tested in the liquid-phase crotonaldehyde hydrogenation reaction. The textural and physicochemical properties of the samples were studied by a series of techniques including XRD, TG-DSC, N2 adsorption–desorption, TEM and HRTEM, IR spectrum, H2-TPD, and H2-TPR. Even after 600 °C reduction, Pt particles of about 0.8–2.8 nm interplayed with support surface to form Pt-doped interface, thereby preventing the catalysts from migration and affording a high dispersion of platinum. The specific exposed crystal-facets and surface oxygen species depending on the shape of the support affected the preferential deposition of Pt species and the metal-support interaction. Thus, Pt catalysts performed different physicochemical properties and catalytic performance relying on the morphology and structure of the supports. During the cycle experiment, severe deactivation was observed for NP-supported catalysts with an increased selectivity due to the aggregation and growth of Pt particles. Meantime, the NR-supported catalysts retained relatively high reactivity as a consequence of the crystal-facet confinement of rod-shaped lanthanum supports.

Hydrogen production by catalytic decalin dehydrogenation over carbon-supported platinum catalyst: Effect of catalyst preparation method

Preparation method strongly affected the platinum dispersion of carbon-supported platinum catalysts, and accordingly, their catalytic activity in the decalin dehydrogenation. The catalyst prepared by an advanced method (ion-exchange method or polyol method) exhibited a better catalytic performance than that prepared by a conventional method (impregnation method or precipitation method) in terms of initial hydrogen evolution rate and total amount of hydrogen evolution. Platinum dispersion played a key role in determining the catalytic activity in this reaction, and thus, the high platinum dispersion of the catalysts prepared by an ion-exchange method and a polyol method resulted in their high catalytic activity.

Synthesis of nanosized platinum based catalyst using sol-gel process

The nano-sized platinum based catalysts using high surface area silica support have been prepared by sol-gel method. Tetramethoxysilane (TMOS) diluted in methanol was hydrolyzed to form a porous silica gel. Platinum (2%) was loaded at sol state using platinum chloride solution. After gelation, the solvent from the gel pores was extracted at ambient temperature which resulted in porous silica matrix incorporated with nanosized platinum. X-ray diffraction studies indicated the presence of elemental platinum in the silica-platinum composites. Transmission electron microscopy of the platinum -silica composites revealed that nanosized platinum particles of about 5-10 nm are homogeneously dispersed in silica matrix. Chemisorptions studies showed high dispersion (more than 50%) of platinum on silica support with specific surface area of 400 m2/g which puts them as promising candidates as catalyst in heterogeneous reactions.

Al(CH3)3-promoted Pt/MCM-41 catalysts for tetralin hydrogenation in the presence of benzothiophene and promotion mechanism of Al-promoted Pt/MCM-41 catalysts

High platinum dispersion benefits tetralin hydrogenation and sulfur tolerance. Sulfur tolerance is also favourable for electron deficient Ptδ+.

Effect of the metal precursor on the properties of Pt/CeO2/C catalysts for the total oxidation of ethanol

Two series of ceria-promoted carbon-supported platinum catalysts have been prepared and evaluated in total oxidation of ethanol, as a model volatile organic compound (VOC), in order to study the effect of the metal precursor (H2PtCl6 or Pt(NH3)4(NO3)2) on their physico-chemical properties and catalytic behavior. Catalysts with Pt loading of 1wt.% and ceria loading of 5, 10 and 20wt.% have been prepared by the impregnation method, and characterized by several techniques (N2 adsorption at 77K, ICP, XRD, H2-TPR and XPS). Toluene hydrogenation has been used to obtain an estimation of the platinum dispersion on the investigated catalysts. On the other hand, their catalytic behavior has been evaluated in the total oxidation of ethanol, selected as a VOCs probe molecule. A much higher catalytic activity and selectivity to CO2 was achieved with chlorinated catalysts. This behavior has been correlated with a high platinum dispersion and a strong metal–CeO2 interaction in these catalysts which promotes their redox properties.

Effect of metal precursors on the performance of Pt/ZSM-22 catalysts for n-hexadecane hydroisomerization

The effects of Pt precursors on the performance of Pt/ZSM-22 catalysts for n-hexadecane hydroisomerization were investigated with 0.5wt.% platinum loading using three platinum precursors: Pt(NO3)2, H2PtCl6, and Pt(NH3)4Cl2. The catalyst derived from H2PtCl6 exhibits the highest platinum dispersion and nPt/nA value and displays better isomerization activity and selectivity. Three effects can be traced back to the precursors: the valence state of Pt, the location of Pt (in cationic or anionic group), and the existence of chloride. The predominant effect is that of valence states of Pt in precursors, which play a crucial role in determining the textural properties (both particle size and crystal structure) of catalysts. Different crystal orientations of Pt0 are found on the reduced samples, with Pt(IV) precursors oriented along the [011] crystallographic axis, while those with Pt(II) precursors are oriented along the [001] axis. The former favors smaller Pt particles and exposes more active Pt{111} corner sites, while the latter exhibits larger Pt particles and exposes more Pt{100} facets, as revealed by combining HRTEM with CO-IR studies. Moreover, Pt{111}/ZSM-22 shows higher isomerization selectivity than Pt{100}/ZSM-22. The other effect is location of Pt in precursors. Compared with the sample using Pt(NH3)4Cl2 precursor, the catalyst with (NH4)2PtCl4 precursor exhibits smaller particles and higher platinum dispersion and facilitates isomerization reactivity. The existence of chloride is also a nonignorable effect. The samples containing chloride ions without amine groups in precursors favor platinum dispersion due to avoiding autoreduction by NH3 during the calcination process.

공기 및 수소 분위기에서 열처리 된 Pt/Al2O3촉매의 HI분해반응 특성

Abstract >> In HI decomposition, Pt/Al 2 O 3 has been studied by several researchers. However, after HI decomposition,it could be seen that metal dispersion of Pt/Al 2 O 3 was greatly decreased. This reason was expected of platinumloss and sintering, which platinum was aggregated. Also, this decrease of metal dispersion caused catalytic deactivation.This study was conducted to find the condition to minimize platinum sintering and loss. In particular, heat treatmentatmosphere and temperature were examined to improve the activity of HI decomposition reaction. First of all,although Pt/Al 2 O 3 treated in hydrogen atmosphere had low platinum dispersion between 13 and 18%, it was shownto suitable platinum form that played an important role in improving HI decomposition reaction. Oxygen in the air atmosphere made Pt/Al 2 O 3 have high platinum dispersion even 61.52% at 500°C. Therefore, in order to get high platinum dispersion and suitable platinum form in HI decomposition reaction, air heat treatment at 500°Cwas needed to add before hydrogen heat treatment. In case of 5A3H, it had 51.13% platinum dispersion and improved HI decomposition reaction activity. Also, after HI decomposition reaction it had considerable platinumdispersion of 23.89%.

ZrO2-SiO2복합산화물에 담지된 백금 촉매의 요오드화수소 분해 특성 연구

This work is investigated for the catalytic decomposition of hydrogen iodide (HI). Platinum was used as active material by loading on <TEX>$ZrO_2-SiO_2$</TEX> mixed oxide in HI decomposition reaction. To obtain high and stable conversion of hydrogen iodide in severe condition, it was required to improve catalytic activity. For this reason, a method increasing dispersion of platinum was proposed in this study. In order to get high dispersion of platinum, zirconia was incorporated in silica by sol-gel synthesis. Incorporating zirconia influence increasing platinum dispersion and BET surface area as well as decreasing deactivation of catalysts. It should be able to stably product hydrogen for a long time because of inhibitive deactivation. HI decomposition reaction was carried out under the condition of <TEX>$450^{\circ}C$</TEX> and 1 atm in a fixed bed reactor. Catalysts analysis methods such as <TEX>$N_2$</TEX> adsorption/desorption analysis, X-ray diffraction, X-ray fluorescence, ICP-AES and CO gas chemisorption were used to measurement of their physico-chemical properties.

Selenium functionalized carbon for high dispersion of platinum–ruthenium nanoparticles and its effect on the electrocatalytic oxidation of methanol

Using selenium functionalized carbon as supports, platinum–ruthenium nanoparticles were highly dispersed on the carbon surface, and showed improved electrochemical properties for methanol electrooxidation. The method provides a new route for functionalization of the carbon surface on which to disperse noble metal nanoparticles for application as electrocatalysts in fuel cells.

Facilely constructing robust nanohybrids comprising high dispersion of platinum–ruthenium nanoparticles on carbon nanotubes and their enhanced electrocatalytic performance

AbstractA method for high dispersion of PtRu nanoparticles (NPs) on carbon nanotubes (CNTs) based on noncovalently functionalized CNTs with dodecylamine (DA) is reported. The process of functionalization of CNTs by DA is simple and can be carried out at room temperature without the use of expensive chemicals or corrosive acids, thus preserving the electronic conductivity and the corrosion resistance of CNTs. PtRu NPs on DA‐functionalized CNTs show much better distribution with no formation of aggregates, higher electrochemically active surface (EAS) area, and higher electrocatalytic activity and stability for the electrooxidation of methanol as compared to that on conventional acid‐oxidized CNTs. magnified image

Binary oxide-doped Pt/RuO2–SiOx/C catalyst with high performance and self-humidification capability: The promotion of ruthenium oxide

A multifunctional catalyst for fuel cell applications, Pt/RuO2–SiOx/C, has been prepared by supporting platinum nanoparticles on surface-modified carbon black, fabricated by in situ hydrolysis of ruthenium and silicon precursors on pre-treated carbon black. The catalyst is extensively characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalyst shows high activity toward methanol oxidation and oxygen reduction at room temperature. Notably, the addition of ruthenium oxide significantly improves the performance of MEAs under non-humidified conditions. The self-humidification performance of MEAs prepared with Pt/RuO2–SiOx/C (using optimized 3wt.% RuO2) as the anode catalyst is enhanced by over 20% compared to MEAs prepared with Pt/SiOx/C as the anode catalyst. It is suggested that the promotion of RuO2 may result from the high dispersion of platinum caused by adding ruthenium oxide, and the synergistic effect of ruthenium oxide.

Platinum catalysts supported on silicas: effect of silica characteristics on their catalytic activity in carbon monoxide oxidation

Platinum catalysts supported on silicas with various physicochemical properties were prepared in order to investigate the effect of silica characteristics on their platinum dispersion and catalytic activity in the oxidation of carbon monoxide. Although titania-incorporation into silica and further treatment of the impregnated platinum precursor with hydrogen peroxide were effective for improving the dispersion and stability of platinum catalysts supported on silicas, regardless of the characteristic of the silicas, the platinum catalysts supported on fumed silica with a medium level of surface hydroxyl group concentration exhibited the highest catalytic activity among those supported on mesoporous silica, silica gel, and precipitated silica. The required properties of the highly active platinum catalyst seemed to be a high dispersion of platinum, the formation of a stable titania layer, and the generation of strong acid sites. By contrast, the precipitated silica with a small surface area and high concentration of surface hydroxyl groups was not appropriate for a catalytic support for platinum catalysts.

Synthesis, characterization and in vitro cytotoxicity of Pt-TiO2 nanoparticles

The adverse toxicological profile of cisplatin (cis-dichlorodiammineplatinum (II)), characterized by nephrotoxicity and neurotoxicity is the main factor that limit the clinical usefulness of this antineoplastic drug, specifically the possibility of applying it in effective high-dose regimens. In order to overcome these disadvantages, many efforts in the search for new drugs have been made. Due to this particularity, we obtained via sol–gel process Pt(acac)2–TiO2 (NPt) nanostructured materials with antitumoral activity to be used as an alternative in the treatment of cancer tumors. The biocatalysts were prepared by the sol–gel route using the complex Pt(acac)2. Sol–gel parameters were controlled in order to obtain high platinum dispersion and particles in the nano-size range. TEM, FTIR, N2 adsorption and XPS characterization studies of the samples were carried out. In order to investigate interactions between the biocatalyst and DNA, agarose gel electrophoresis was performed, and we observed the formation of DNA adducts. 45 minutes after contact, NPt completely degraded the DNA (cisplatin 120 minutes). These results demonstrate that using a metal supported and dispersed over an inorganic biocompatible oxide, can be effectively used in the treatment of localized tumors.