scholarly journals Model Catalysis with HOPG-Supported Pd Nanoparticles and Pd Foil: XPS, STM and C2H4 Hydrogenation

2021 ◽  
Author(s):  
Md. Abdul Motin ◽  
Andreas Steiger-Thirsfeld ◽  
Michael Stöger-Pollach ◽  
Günther Rupprechter
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Characteristics ◽  
Pd Nanoparticles ◽  
Activation Energies ◽  
Model Systems ◽  
Scanning Tunneling ◽  
Nucleation Density ◽  
Height Distribution ◽  
Before And After ◽  
Supported Pd

AbstractA surface science based approach was applied to model carbon supported Pd nanoparticle catalysts. Employing physical vapour deposition of Pd on sputtered surfaces of highly oriented pyrolytic graphite (HOPG), model catalysts were prepared that are well-suited for characterization by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Analysis of the HOPG substrate before and after ion-bombardment, and of Pd/HOPG before and after annealing, revealed the number of “nominal” HOPG defects (~ 1014 cm−2) as well as the nucleation density (~ 1012 cm−2) and structural characteristics of the Pd nanoparticles (mean size/height/distribution). Two model systems were stabilized by UHV annealing to 300 °C, with mean Pd particles sizes of 4.3 and 6.8 nm and size/height aspect ratio up to ~ 10. A UHV-compatible flow microreactor and gas chromatography were used to determine the catalytic performance of Pd/HOPG in ethylene (C2H4) hydrogenation up to 150 °C under atmospheric pressure, yielding temperature-dependent conversion values, turnover frequencies (TOFs) and activation energies. The performance of Pd nanocatalysts is compared to that of polycrystalline Pd foil and contrasted to Pt/HOPG and Pt foil, pointing to a beneficial effect of the metal/carbon phase boundary, reflected by up to 10 kJ mol−1 lower activation energies for supported nanoparticles. Graphical Abstract

scholarly journals Supports and modified nano-particles for designing model catalysts

2016 ◽  
Vol 188 ◽  
pp. 309-321 ◽  
Author(s):  
C. P. O'Brien ◽  
K.-H. Dostert ◽  
M. Hollerer ◽  
C. Stiehler ◽  
F. Calaza ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Pd Nanoparticles ◽  
Metal Nanoparticle ◽  
Model Systems ◽  
Nano Particles ◽  
Structure Changes ◽  
Hydrogenation Reactions ◽  
Composite Nature ◽  
Specific Reactions ◽  
Supported Pd

In order to design catalytic materials, we need to understand the essential causes for material properties resulting from its composite nature. In this paper we discuss two, at first sight, diverse aspects: (a) the effect of the oxide–metal interface on metal nanoparticle properties and (b) the consequences of metal particle modification after activation on the selectivity of hydrogenation reactions. However, these two aspects are intimately linked. The metal nanoparticle’s electronic structure changes at the interface as a catalyst is brought to different reaction temperatures due to morphological modifications in the metal and, as we will discuss, these changes in the chemistry lead to changes in the reaction path. As the morphology of the particle varies, facets of different orientations and sizes are exposed, which may lead to a change in the surface chemistry as well. We use two specific reactions to address these issues in some detail. To the best of our knowledge, the present paper reports the first observations of this kind for well-defined model systems. The changes in the electronic structure of Au nanoparticles due to their size and interaction with a supporting oxide are revealed as a function of temperature using CO2 activation as a probe. The presence of spectator species (oxopropyl), formed during an activation step of acrolein hydrogenation, strongly controls the selectivity of the reaction towards hydrogenation of the unsaturated CO bond vs. the CC bond on Pd(111) when compared with oxide-supported Pd nanoparticles.

STRUCTURE, THERMAL STABILITY, AND CO ADSORPTION PROPERTIES OF PD NANOPARTICLES SUPPORTED ON AN ULTRA-THIN SiO2 FILM

2007 ◽  
Vol 14 (05) ◽  
pp. 927-934 ◽  
Author(s):  
J.-L. LU ◽  
J. WEISSENRIEDER ◽  
S. KAYA ◽  
H.-J. GAO ◽  
S. SHAIKHUTDINOV ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Elevated Temperatures ◽  
Morphological Changes ◽  
Co Adsorption ◽  
Pd Nanoparticles ◽  
Silica Film ◽  
Adsorption Properties ◽  
Scanning Tunneling ◽  
Tunneling Microscopy

Nucleation, growth, and thermal stability of Pd particles vapor-deposited on an ultra-thin crystalline silica film grown on Mo (112) have been studied by scanning tunneling microscopy, X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and temperature-programmed desorption of CO . No preferential nucleation of Pd on the silica film is found at room temperature deposition: the hemispherical Pd nanoparticles are homogenously dispersed on the support at all coverages studied (0.01 - 1 ML (mono layer)). The Pd particles are resistant toward sintering up to 700 K as judged by STM; however, CO adsorption studies have revealed surface chemical modification at temperatures as low as 550 K. Strong morphological changes are observed above 800 K (ultimately resulting in elongated rectangular islands at ~1000 K), which is accompanied by strong alterations of CO adsorption properties. The results are rationalized in terms of Pd and Mo substrate interdiffusion at elevated temperatures, while the silica film basically preserves its structure.

Stability of Nanopyramids of Pt/W(111) in Sulfuric Acid Medium

2017 ◽  
Vol 735 ◽  
pp. 219-224
Author(s):  
Mohammad K. El Jawad ◽  
Bruno Gilles ◽  
Frederic Maillard
Keyword(s):  
Sulfuric Acid ◽  
Electrochemical Behavior ◽  
Photoelectron Spectroscopy ◽  
Oxidation Process ◽  
Electrochemical Measurements ◽  
Scanning Tunneling ◽  
X Ray ◽  
Sulfuric Acid Medium ◽  
Before And After ◽  
Stm Images

We report on the electrochemical behavior of Pt/W(111) nanfaceted surface in sulfuric acid. The Pt/W(111) nanofaceted surface was characterized by X-ray photelectron spectroscopy (XPS) and Scanning Tunneling Micrsocopy (STM) before and after the electrochemical measurements. The X-ray photoelectron spectroscopy (XPS) have shown a partial oxidation of W(111) during electrochemical measurements. Comparison of STM images before and after the electrochemical measurements enabled to locate the region where the oxidation process took place.

scholarly journals SYNTHESIS OF Pd-CONTAINING HYPERCROSSLINKED POLYSTYRENE AND RESEARCH OF ITS CATALYTIC PROPERTIES FOR FURFURAL HYDROGENATION

2018 ◽  
Vol 59 (4) ◽  
pp. 59
Author(s):  
Valentin Yu. Doluda ◽  
Viktoriya A. Strigina ◽  
Valentina G. Matveeva ◽  
Esfir M. Sul’man ◽  
Natalia V. Lakina
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalytic Properties ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Pd Nanoparticles ◽  
Hypercrosslinked Polystyrene ◽  
X Ray ◽  
Physical Chemical ◽  
Polystyrene Matrix ◽  
Furfural Hydrogenation

In this paper the results were presented on the study of physical-chemical and catalytic properties of Pd nanoparticles synthesized in hypercrosslinked polystyrene matrix with various methods allowing to obtain Pd particles of different sizes. Obtained samples were sudied with the methods of chemisorption of hydrogen, nitrogen adsorption, X-ray photoelectron spectroscopy. Synthesized catalysts were tested in the reaction of catalytic furfural hydrogenation. The dependence of the catalysts activity on their structural characteristics was determined.

scholarly journals Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite

2021 ◽  
Vol 30 ◽  
pp. 2633366X2097865
Author(s):  
Li Jian
Keyword(s):  
Shear Strength ◽  
Surface Treatment ◽  
Photoelectron Spectroscopy ◽  
Resin Composite ◽  
Contact Angles ◽  
Static Contact ◽  
Before And After ◽  
C Value ◽  
Interlayer Shear Strength ◽  
Pmma Resin

The surface treatment of carbon fibers (CFs) was carried out using a self-synthesized sizing agent. The effects of sizing agent on the surface of CFs and the interface properties of CF/polymethyl methacrylate (PMMA) composites were mainly studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and static contact angle were used to compare and study the CFs before and after the surface treatment, including surface morphology, surface chemical element composition, and wettability of the surface. The influence of sizing agent on the mechanical properties of CF/PMMA resin composite interface was investigated. The results show that after sizing treatment, the CF surface O/C value increased by 35.1% and the contact angles of CF and resin decreased by 16.2%. The interfacial shear strength and interlayer shear strength increased by 12.6%.

Monodisperse-porous cerium oxide microspheres as a new support with appreciable catalytic activity for a composite catalyst in benzyl alcohol oxidation

2021 ◽  
Author(s):  
Kadriye Özlem Hamaloğlu ◽  
Rukiye Babacan Tosun ◽  
Serap Ulu ◽  
Hakan Kayi ◽  
Cengiz Kavaklı ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Benzyl Alcohol ◽  
Cerium Oxide ◽  
Sol Gel ◽  
Alcohol Oxidation ◽  
Pd Nanoparticles ◽  
Composite Catalyst ◽  
Benzyl Alcohol Oxidation ◽  
Supported Pd

A synergistic catalyst in the form of monodisperse-porous CeO2 microspheres supported Pd nanoparticles (Pd NPs) was synthesized. CeO2 microspheres 4 μm in size were obtained by a newly developed “sol-gel...

scholarly journals Ordered Mesoporous Carbon as a Support for Palladium-Based Hydrodechlorination Catalysts

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Farzeen Sakina ◽  
Carlos Fernandez-Ruiz ◽  
Jorge Bedia ◽  
Luisa Gomez-Sainero ◽  
Richard Baker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Mesoporous Carbon ◽  
Catalyst Deactivation ◽  
Average Diameter ◽  
Pd Nanoparticles ◽  
Ordered Mesoporous Carbon ◽  
Catalyst Composition ◽  
Ordered Mesoporous ◽  
Higher Hydrocarbons ◽  
Carbon Catalysts

Ordered mesoporous carbon (OMC) was employed as a support for palladium nanoparticles in catalysts for the gas phase hydrodechlorination (HDC) of trichloromethane (TCM). 1 wt% palladium was incorporated using three methods: incipient wetness (IW); a dilute solution (DS) method; and a solid-liquid (SL) method. The effect of the preparation method on catalyst structure and activity was investigated. Catalyst composition and nanostructure were studied using gas physisorption, high specification transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic conversion and product selectivities were determined in steady-state activity tests at temperatures between 70 and 300 °C. Two of the catalysts (IW and DS) showed excellent dispersion of fine Pd nanoparticles of average diameter ~2 nm. These materials showed excellent activity for HDC of TCM which compares favourably with the performance reported for Pd on amorphous carbon catalysts. In addition, they showed relatively high selectivities to the more valuable higher hydrocarbons. However, the SL method gave rise to catalysts with larger particles (~3 nm) and a less uniform palladium distribution. This resulted in lower conversion and lower selectivities to higher hydrocarbons and in more severe catalyst deactivation at the highest reaction temperatures.

scholarly journals Synthesis of Novel Arginine-Based Flame Retardant and Its Application in Lyocell Fabric

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3588
Author(s):  
Jiayi Chen ◽  
Yansong Liu ◽  
Jiayue Zhang ◽  
Yuanlin Ren ◽  
Xiaohui Liu
Keyword(s):  
Fourier Transform ◽  
Heat Release ◽  
Flame Retardant ◽  
Photoelectron Spectroscopy ◽  
Fourier Transform Infrared ◽  
Ftir Analysis ◽  
Excellent Thermal Stability ◽  
X Ray ◽  
Cone Calorimeter Test ◽  
Before And After

Lyocell fabrics are widely applied in textiles, however, its high flammability increases the risk of fire. Therefore, to resolve the issue, a novel biomass-based flame retardant with phosphorus and nitrogen elements was designed and synthesized by the reaction of arginine with phosphoric acid and urea. It was then grafted onto the lyocell fabric by a dip-dry-cure technique to prepare durable flame-retardant lyocell fabric (FR-lyocell). X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated that the flame retardant was successfully introduced into the lyocell sample. Thermogravimetric (TG) and Raman analyses confirmed that the modified lyocell fabric featured excellent thermal stability and significantly increased char residue. Vertical combustion results indicated that FR-lyocell before and after washing formed a complete and dense char layer. Thermogravimetric Fourier-transform infrared (TG-FTIR) analysis suggested that incombustible substances (such as H2O and CO2) were produced and played a significant fire retarding role in the gas phase. The cone calorimeter test corroborated that the peak of heat release rate (PHRR) and total heat release (THR) declined by 89.4% and 56.4%, respectively. These results indicated that the flame retardancy of the lyocell fabric was observably ameliorated.

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