News & Scientific Highlights


Unravelling the amorphous structure and crystallization mechanism of GeTe phase change memory materials

Here we use in-situ high-temperature x-ray absorption spectroscopy (XAS) and theoretical calculations to quantify the amorphous structure of bulk and nanoscale GeTe. Based on XAS experiments, we develop a theoretical model of the amorphous GeTe structure, consisting of a disordered fcc-type Te sublattice and randomly arranged chains of Ge atoms in a tetrahedral coordination.

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acetylene hydrochlorination active sites

Evidence of bifunctionality of carbons and metal atoms in catalyzed acetylene hydrochlorination

Carbon supports are ubiquitous components of heterogeneous catalysts for acetylene hydrochlorination to vinyl chloride, from commercial mercury-based systems to more sustainable metal single-atom alternatives. Their potential co-catalytic role has long been postulated but never unequivocally demonstrated. Herein, combining operando X-ray absorption spectroscopy with other spectroscopic and kinetic analyses, we evidence the bifunctionality of carbons and metal sites (Pt, Au, Ru) in the acetylene hydrochlorination catalytic cycle.

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Deciphering the Mechanism of Crystallization of UiO-66 Metal-Organic Framework

Zirconium-containing metal-organic framework (MOF) with UiO-66 topology is an extremely versatile material, which finds applications beyond gas separation and catalysis.  By means of in situ time-resolved high-resolution mass spectrometry, Zr K-edge X-ray absorption spectroscopy, magic-angle spinning nuclear magnetic resonance spectroscopy, and X-ray diffraction it is showed that the nucleation of UiO-66 occurs via a solution-mediated hydrolysis of zirconium chloroterephthalates, whose formation appears to be autocatalytic.

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Activity Trend Origin of Ethanol Oxidative Dehydrogenation over VOx/CeO2

Using operando time-resolved X-ray absorption spectroscopy, we investigated the origin of volcano-shaped ethanol oxidative dehydrogenation activity trend of VOx/CeO2 catalysts as a function of VOx surface coverage. Vanadium and cerium synergistically change their oxidation states during the catalytic cycle. The catalytic activity correlates with the concentration of reversible Ce4+/3+species.

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Pd Hydrides on Pd/Al2O3 in Liquid Environment

Preparation, Quantification, and Reaction of Pd Hydrides on Pd/Al2O3 in Liquid Environment

The ability to study in situ the formation and consumption of Pd hydrides (PdH) in liquid environments is a significant challenge hampering a deeper understanding of catalyzed liquid-phase hydrogenation reactions. Here, using quick scanning X-ray absorption spectroscopy (QEXAFS), we present a detailed kinetic study of Pd hydride formation and reactivity on Pd/Al2O3 in 2-propanol solvent. 

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Catalyst Layer Thickness Effects on Operando/In Situ Measurements

Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements

Operando/in situ spectro-electrochemical studies often require high loadings and thick catalyst layers (CLs) leading to large ion- and mass-transport limitations. In this study we investigate PdH-formation in two Pd-catalysts with similar surface areas but drastically different morphologies. Our results unveil that the CL-thickness largely determines the PdH formation trends calling for the minimization of the CL-thickness in such experiments.

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Platinum-Iron(II) Oxide Sites Directly Responsible for Preferential Carbon Monoxide Oxidation at Ambient Temperature: An Operando X-ray Absorption Spectroscopy Study

Operando X-ray absorption spectroscopy revealed a linear correlation between the amount of oxidic Fe2+ and the ambient temperature activity of Pt−FeOx preferential carbon monoxide oxidation catalysts. The hydrogen prereduction temperature and pressure determines the amount of active Fe2+ sites for alumina- and silica-supported Pt−Fe catalysts. Catalyst deactivation is linked with the oxidation of these sites.

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Quantifying Photoinduced Polaronic and Thermal Distortions in Inorganic Lead Halide Perovskite Nanocrystals

The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding of the interaction between charge carriers and the polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that the Pb–Br framework flexibility plays a key role in their light-activated functionality, the corresponding local structural rearrangement has not yet been unambiguously identified. In this work the photoinduced lattice changes were investigated using combination of time-resolved and temperature-dependent studies at Br K and Pb L3 X-ray absorption edges and ab initio simulations.

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