High-Temperature Behavior of Pd/MgO Catalysts Prepared via Various Sol-Gel Approaches.

A series of Pd/MgO catalysts based on nanocrystalline MgO were prepared via different sol-gel approaches. In the first two cases, palladium was introduced during the gel preparation, followed by drying it in supercritical or ambient conditions. In the third case, aerogel-prepared MgO was impregnated with an ethanol solution of Pd(NO).

Thermally Induced Surface Structure and Morphology Evolution in Bimetallic Pt-Au/HOPG Nanoparticles as Probed Using XPS and STM.

Bimetallic nanoparticles expand the possibilities of catalyst design, providing an extra degree of freedom for tailoring the catalyst structure in comparison to purely monometallic systems. The distribution mode of two metal species defines the structure of surface catalytic sites, and current research efforts are focused on the development of methods for their controlled tuning. In light of this, a comprehensive investigation of the factors which influence the changes in the morphology of bimetallic nanoparticles, including the elemental redistribution, are mandatory for each particular bimetallic system.

Combining Atomic Layer Deposition with Surface Organometallic Chemistry to Enhance Atomic-Scale Interactions and Improve the Activity and Selectivity of Cu-Zn/SiO Catalysts for the Hydrogenation of CO to Methanol.

The direct synthesis of methanol via the hydrogenation of CO, if performed efficiently and selectively, is potentially a powerful technology for CO mitigation. Here, we develop an active and selective Cu-Zn/SiO catalyst for the hydrogenation of CO by introducing copper and zinc onto dehydroxylated silica via surface organometallic chemistry and atomic layer deposition, respectively. At 230 °C and 25 bar, the optimized catalyst shows an intrinsic methanol formation rate of 4.

Hybrid Nanocomposite Solid Electrolytes (n-CH)NBF-MgO.

Hybrid nanocomposite materials BuNBF-MgO were obtained using a nanocrystalline MgO with a specific surface area of 324 m/g and the grains size of 5.1 nm. As a result of the strong adhesion, the salt transforms into an interface-stabilized amorphous state within the thin layer near the interface.

Kinetic Aspects of Benzene Degradation over TiO-N and Composite Fe/BiWO/TiO-N Photocatalysts under Irradiation with Visible Light.

In this study, composite materials based on nanocrystalline anatase TiO doped with nitrogen and bismuth tungstate are synthesized using a hydrothermal method. All samples are tested in the oxidation of volatile organic compounds under visible light to find the correlations between their physicochemical characteristics and photocatalytic activity. The kinetic aspects are studied both in batch and continuous-flow reactors, using ethanol and benzene as test compounds.

Atomic-scale changes of silica-supported catalysts with nanocrystalline or amorphous gallia phases: implications of hydrogen pretreatment on their selectivity for propane dehydrogenation.

This work explores how H pretreatment at 550 °C induces structural transformation of two gallia-based propane dehydrogenation (PDH) catalysts, nanocrystalline γ/β-GaO and amorphous GaO (GaO ) supported on silica (γ-GaO/SiO and Ga/SiO, respectively) and how it affects their activity, propene selectivity and stability with time on stream (TOS). Ga/SiO-H shows poor activity and propene selectivity, no coking and no deactivation with TOS, similar to Ga/SiO. In contrast, the high initial activity and propene selectivity of γ-GaO/SiO-H decline with TOS but to a lesser extent than in calcined γ-GaO/SiO.

Composite photocatalysts based on Cd Zn S and TiO for hydrogen production under visible light: effect of platinum co-catalyst location.

Ternary composite photocatalysts based on titania and solid solutions of CdS and ZnS were prepared and studied by a set of physicochemical methods including XRD, XPS, HRTEM, UV-vis spectroscopy, and electrochemical tests. Two synthetic techniques of platinization of Cd Zn S/TiO were compared. In the first case, platinum was deposited on the surface of synthesized Cd Zn S ( = 0.

Near-Ambient Pressure XPS and MS Study of CO Oxidation over Model Pd-Au/HOPG Catalysts: The Effect of the Metal Ratio.

In this study, the dependence of the catalytic activity of highly oriented pyrolytic graphite (HOPG)-supported bimetallic Pd-Au catalysts towards the CO oxidation based on the Pd/Au atomic ratio was investigated. The activities of two model catalysts differing from each other in the initial Pd/Au atomic ratios appeared as distinctly different in terms of their ignition temperatures. More specifically, the PdAu-2 sample with a lower Pd/Au surface ratio (~0.

Liquid-Phase Hydrogenation of 1-Phenyl-1-propyne on the PdAg/AlO Single-Atom Alloy Catalyst: Kinetic Modeling and the Reaction Mechanism.

This research was focused on studying the performance of the PdAg/AlO single-atom alloy (SAA) in the liquid-phase hydrogenation of di-substituted alkyne (1-phenyl-1-propyne), and development of a kinetic model adequately describing the reaction kinetic being also consistent with the reaction mechanism suggested for alkyne hydrogenation on SAA catalysts. Formation of the SAA structure on the surface of PdAg nanoparticles was confirmed by DRIFTS-CO, revealing the presence of single-atom Pd sites surrounded by Ag atoms (characteristic symmetrical band at 2046 cm) and almost complete absence of multiatomic Pd surface sites (<0.2%).

Synthesis, Characterization and Visible-Light Photocatalytic Activity of Solid and TiO-Supported Uranium Oxycompounds.

In this study, various solid uranium oxycompounds and TiO-supported materials based on nanocrystalline anatase TiO are synthesized using uranyl nitrate hexahydrate as a precursor. All uranium-contained samples are characterized using N adsorption, XRD, UV-vis, Raman, TEM, XPS and tested in the oxidation of a volatile organic compound under visible light of the blue region to find correlations between their physicochemical characteristics and photocatalytic activity. Both uranium oxycompounds and TiO-supported materials are photocatalytically active and are able to completely oxidize gaseous organic compounds under visible light.

Mechanistic in situ investigation of heterogeneous hydrogenation over Rh/TiO catalysts: selectivity, pairwise route and catalyst nature.

The selectivity of product formation is strongly correlated with the nature of the catalyst active centers. Therefore, the selective synthesis of active sites with certain structure is a big challenge in modern catalysis. Here synthetic procedures are adopted for the formation of 1% Rh/TiO catalysts with different properties.

Tetranitratopalladate(II) Salts with Tetraalkylammonium Cations: Structural Aspects, Reactivity, and Applicability toward Palladium Deposition for Catalytic Applications.

A series of salts (RN)[Pd(NO)] (R = CH, CH, n-CH; -) were synthesized in high yield from a nitric acid solution of palladium. The salts were characterized by a combination of physicochemical methods, and their crystal structures were determined by X-ray diffraction. The conformation of the [Pd(NO)] anion was studied in detail using crystal structure data and density functional theory calculations.

Comparative Study of the Photocatalytic Hydrogen Evolution over CdMnS and CdS-β-MnO-MnOOH Photocatalysts under Visible Light.

A series of solid solutions of cadmium and manganese sulfides, CdMnS (x = 0-0.35), and composite photocatalysts, CdS-β-MnO-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N low temperature adsorption.

Pd Single-Atom Sites on the Surface of PdAu Nanoparticles: A DFT-Based Topological Search for Suitable Compositions.

Structure of model bimetallic PdAu nanoparticles is analyzed aiming to find Pd:Au ratios optimal for existence of Pd1 single-atom surface sites inside outer Au atomic shell. The analysis is performed using density-functional theory (DFT) calculations and topological approach based on DFT-parameterized topological energy expression. The number of the surface Pd1 sites in the absence of adsorbates is calculated as a function of Pd concentration inside the particles.

An ultrahigh vacuum-compatible reaction cell for model catalysis under atmospheric pressure flow conditions.

Atmospheric pressure reactions on model catalysts are typically performed in so-called high-pressure cells, with product analysis performed by gas chromatography (GC) or mass spectrometry (MS). However, in most cases, these cells have a large volume (liters) so that the reactions on catalysts with only cm surface area can be carried out only in the (recirculated) batch mode to accumulate sufficient product amounts. Herein, we describe a novel small-volume (milliliters) catalytic reactor that enables kinetic studies under atmospheric pressure flow conditions.

Photoinduced Deposition of Platinum from (BuN)[Pt(NO)] for a Low Pt-Loading Pt/TiO Hydrogen Photogeneration Catalyst.

An efficient method for the deposition of ionic platinum species PtO onto a TiO surface was developed on the basis of light-induced activation of the [Pt(NO)] anion. The deposited PtO species with an effective Pt oxidation state between +4 and +2 have an oxygen-made environment and include single ion centers {PtO} and polyatomic ensembles {PtO} connected to a TiO surface with Pt-O-Ti bonds. The resulting PtO/TiO materials were tested as photocatalysts for the hydrogen evolution reaction (HER) from a water ethanol mixture and have shown uniquely high activity with the rate of H evolution achieving 11 mol h per gram of Pt, which is the highest result for such materials reported to date.

Selective Single-Site Pd-In Hydrogenation Catalyst for Production of Enhanced Magnetic Resonance Signals using Parahydrogen.

Pd-In/Al O single-site catalyst was able to show high selectivity (up to 98 %) in the gas phase semihydrogenation of propyne. Formation of intermetallic Pd-In compound was studied by XPS during reduction of the catalyst. FTIR-CO spectroscopy confirmed single-site nature of the intermetallic Pd-In phase reduced at high temperature.

Aqueous, Heterogeneous Parahydrogen-Induced N Polarization.

The successful transfer of parahydrogen-induced polarization to N spins using heterogeneous catalysts in aqueous solutions was demonstrated. Hydrogenation of a synthesized unsaturated N-labeled precursor (neurine) with parahydrogen (p-H) over Rh/TiO heterogeneous catalysts yielded a hyperpolarized structural analog of choline. As a result, N polarization enhancements of over two orders of magnitude were achieved for the N-ethyl trimethyl ammonium ion product in deuterated water at elevated temperatures.

Heterogeneous Microtesla SABRE Enhancement of N NMR Signals.

The hyperpolarization of heteronuclei via signal amplification by reversible exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes=1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD=cyclooctadiene] catalyst onto silica particles modified with amine linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate a circa 100-fold enhancement of N NMR signals in N-pyridine at 9.4 T following parahydrogen bubbling within a magnetic shield.

Production of Pure Aqueous C-Hyperpolarized Acetate by Heterogeneous Parahydrogen-Induced Polarization.

A supported metal catalyst was designed, characterized, and tested for aqueous phase heterogeneous hydrogenation of vinyl acetate with parahydrogen to produce C-hyperpolarized ethyl acetate for potential biomedical applications. The Rh/TiO catalyst with a metal loading of 23.2 wt % produced strongly hyperpolarized C-enriched ethyl acetate-1- C detected at 9.

CO Adsorption on Reconstructed Ir(100) Surfaces from UHV to mbar Pressure: A LEED, TPD, and PM-IRAS Study.

Clean and stable surface modifications of an iridium (100) single crystal, i.e., the (1 × 1) phase, the (5 × 1) reconstruction, and the oxygen-terminated (2 × 1)-O surface, were prepared and characterized by low energy electron diffraction (LEED), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS) and polarization modulation IRAS (PM-IRAS).