Steering the Methane Dry Reforming Reactivity of Ni/LaO Catalysts by Controlled In Situ Decomposition of Doped LaNiO Precursor Structures.

The influence of A- and/or B-site doping of Ruddlesden-Popper perovskite materials on the crystal structure, stability, and dry reforming of methane (DRM) reactivity of specific ABO phases (A = La, Ba; B = Cu, Ni) has been evaluated by a combination of catalytic experiments, in situ X-ray diffraction, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and aberration-corrected electron microscopy. At room temperature, B-site doping of LaNiO with Cu stabilizes the orthorhombic structure () of the perovskite, while A-site doping with Ba yields a tetragonal space group (4/). We observed the orthorhombic-to-tetragonal transformation above 170 °C for LaNiCuO and LaNiCuO, slightly higher than for undoped LaNiO.

Zirconium Oxycarbide: A Highly Stable Catalyst Material for Electrochemical Energy Conversion.

Metal carbides and oxycarbides have recently gained considerable interest due to their (electro)catalytic properties that differ from those of transition metals and that have potential to outperform them as well. The stability of zirconium oxycarbide nanopowders (ZrO C ), synthesized via a hybrid solid-liquid route, is investigated in different gas atmospheres from room temperature to 800 °C by using in-situ X-ray diffraction and in-situ electrical impedance spectroscopy. To feature the properties of a structurally stable Zr oxycarbide with high oxygen content, a stoichiometry of ZrO C has been selected.

Real-time direct transmission electron microscopy imaging of phase and morphology transformation from solid indium oxide hydroxide to hollow corundum-type indium oxide nanocrystallites.

A time-resolved series of high-resolution transmission electron microscopy (HRTEM) images are used to monitor phase and morphology transformation of rod-like and spherical particles with the initial orthorhombic InOOH phase in situ under continuous illumination with high-energy electrons in a transmission electron microscope. For both particle types, the electron-beam irradiation induces a fast InOOH to rh-InO decomposition accompanied by the formation of voids within the particle/rod center. After illumination time intervals of about 1-2 min (i.

Reactive metal-support interaction in the Cu-InO system: intermetallic compound formation and its consequences for CO-selective methanol steam reforming.

The reactive metal-support interaction in the Cu-InO system and its implications on the CO selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic InO support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on InO. This system already represents a highly CO-selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H formation rate of 1.

On the structural stability of crystalline ceria phases in undoped and acceptor-doped ceria materials under reduction conditions.

The reduction of pure and Sm-doped ceria in hydrogen has been studied by synchrotron-based X-ray diffraction to eventually prove or disprove the presence of crystalline cerium hydride (CeH ) phases and the succession of potential structural phase (trans)formations of reduced cerium oxide phases during heating-cooling cycles up to 1273 K. Despite a recent report on the existence of bulk and surface CeH phases during reductive treatment of pure CeO in H, structural analysis by Rietveld refinement as well as additional H-NMR spectroscopy did not reveal the presence of any crystalline CeH phase. Rather, a sequence of phase transformations during the re-cooling process in H has been observed.

Crystallographic and electronic evolution of lanthanum strontium ferrite (LaSrFeO) thin film and bulk model systems during iron exsolution.

We study the changes in the crystallographic phases and in the chemical states during the iron exsolution process of lanthanum strontium ferrite (LSF, La0.6Sr0.4FeO3-δ).

Zirconium-Assisted Activation of Palladium To Boost Syngas Production by Methane Dry Reforming.

C-saturated Pd nanoparticles with an extended phase boundary to ZrO evolve from a Pd Zr precatalyst under CH dry reforming conditions. This highly active catalyst state fosters bifunctional action: CO is efficiently activated at oxidic phase boundary sites and Pd C provides fast supply of C-atoms toward the latter.

H reduction of Gd- and Sm-doped ceria compared to pure CeO at high temperatures: effect on structure, oxygen nonstoichiometry, hydrogen solubility and hydroxyl chemistry.

The effect of Gd- and Sm-doping on pure CeO2 with respect to crystal structure, oxygen nonstoichiometry, hydrogen solubility and hydroxyl chemistry in a hydrogen atmosphere at elevated temperatures was studied using a combination of powder X-ray diffraction (XRD), temperature-programmed methods (such as reduction, desorption and oxidation), and Fourier-Transform Infrared Spectroscopy (FT-IR). In particular, Gd0.1Ce0.

Transmission in situ and operando high temperature X-ray powder diffraction in variable gaseous environments.

This work describes a device for time-resolved synchrotron-based in situ and operando X-ray powder diffraction measurements at elevated temperatures under controllable gaseous environments. The respective gaseous sample environment is realized via a gas-tight capillary-in-capillary design, where the gas flow is achieved through an open-end 0.5 mm capillary located inside a 0.

Ferrimagnetism in manganese-rich gallium and aluminium spinels due to mixed valence Mn-Mn states.

Stoichiometric (MnGaO and MnAlO) and Mn-rich (MnGaO and MnAlO) spinels with a small inversion degree (0.14-0.21) were obtained via a co-precipitation route followed by calcination of the as-synthesized coprecipitates at 700-1000 °C under different gas atmospheres (air, N or argon).

Structural investigations of LaSrFeO under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena.

The crystal structure changes and iron exsolution behavior of a series of oxygen-deficient lanthanum strontium ferrite (LaSrFeO , LSF) samples under various inert and reducing conditions up to a maximum temperature of 873 K have been investigated to understand the role of oxygen and iron deficiencies in both processes. Iron exsolution occurs in reductive environments at higher temperatures, leading to the formation of Fe rods or particles at the surface. Utilizing multiple and methods ( X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning X-ray absorption near-edge spectroscopy (XANES)), the thermodynamic and kinetic limitations are accordingly assessed.

Surface chemistry and stability of metastable corundum-type InO.

To account for the explanation of an eventual sensing and catalytic behavior of rhombohedral InO (rh-InO) and the dependence of the metastability of the latter on gas atmospheres, in situ electrochemical impedance spectroscopic (EIS), Fourier-transform infrared spectroscopic (FT-IR), in situ X-ray diffraction and in situ thermogravimetric analyses in inert (helium) and reactive gases (hydrogen, carbon monoxide and carbon dioxide) have been conducted to link the gas-dependent electrical conductivity features and the surface chemical properties to its metastability towards cubic InO. In particular, for highly reducible oxides such as InO, for which not only the formation of oxygen vacancies, but deep reduction to the metallic state (i.e.

Surface chemistry of pure tetragonal ZrO and gas-phase dependence of the tetragonal-to-monoclinic ZrO transformation.

The surface chemical properties of undoped tetragonal ZrO and the gas-phase dependence of the tetragonal-to-monoclinic transformation are studied using a tetragonal ZrO polymorph synthesized via a sol-gel method from an alkoxide precursor. The obtained phase-pure tetragonal ZrO is defective and strongly hydroxylated with pronounced Lewis acidic and Brønsted basic surface sites. Combined in situ FT-infrared and electrochemical impedance measurements reveal effective blocking of coordinatively unsaturated sites by both CO and CO, as well as low conductivity.