Scientific Highlights

Datum
18. Februar 2021
Platinum chloride in aqueous solution promotes the dispersion of large gold nanoparticles (>70 nm) on carbon

Sustainable Synthesis of Bimetallic Single Atom Gold-Based Catalysts with Enhanced Durability in Acetylene Hydrochlorination

Platinum chloride in aqueous solution promotes the dispersion of large gold nanoparticles (>70 nm) on carbon carriers into single atoms, forming bimetallic single-atom catalysts with improved resistance against sintering at temperatures up to 800 K and under the harsh reductive reaction conditions of acetylene hydrochlorination, leading to improved lifetime in this reaction. To rationalize these observations, this study, led by ETH Zurich, utilized X-ray adsorption spectroscopy conducted at the SuperXAS beamline of the SLS to provide insights into the degree of gold dispersion and the structure of the isolated metal sites in the bimetallic catalysts.

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2. Dezember 2020
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Key activity descriptors of nickel-iron oxygen evolution electrocatalysts in the presence of alkali metal cations

Ni-Fe oxyhydroxide is among the most active oxygen evolution electrocatalysts. Electrolyte alkali metal cations modify the activity and reaction intermediates, however, the exact mechanism is at question due to unexplained deviations from the cation size trend. Our X-ray absorption spectroelectrochemical results show that the OER activity follows the variations in .electrolyte pH rather than a specific cation. Our DFT-based reactivity descriptors confirm the conclusions of an indirect pH effect.

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31. August 2020
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The structure of active sites of CoMo/Al2O3 catalysts determined by RIXS spectroscopy.

A fundamental understanding of the active sites in technical CoMo/ Al2O3 catalysts is crucial to improve the production of clean transportation fuels by hydrodesulfurization (HDS), which removes sulfur from fossil fuels. Sulfur dioxide, resulting from fossil fuel combustion, is one of the main causes for acid rain. In situ X-ray spectroscopic experiments at the SuperXAS beamline of the SLS provided insight in the structure and number of active sites (“Co−Mo−S”) in sulfided CoMo/ Al2O3 catalysts. When the Co to Mo ratio is less than 0.1, cobalt forms isolated sites on the MoS2 phase, where the cobalt promoter atoms are in centrosymmetric octahedral coordination with six-sulfur ligands.

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1. Mai 2020
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Taking a snapshot of the triplet excited state of an OLED organometallic luminophore using X-rays

In this work, the complementarity of pump-probe experiments at SwissFEL (ALVRA endstation) and at synchrotrons (SuperXAS beamline of SLS and ID09 of ESRF) is used to investigate the triplet excited state of Cu OLED materials. Details about the charge transfer and structural rearrangements in the excited state of this material are revealed and obtained data can be used to verify computational methods for rational development of new OLED materials.

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25. März 2020
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Elucidating the Oxygen Activation Mechanism on Ceria-Supported Copper-Oxo Species Using Time-Resolved X-ray Absorption Spectroscopy

We monitored the dynamic structure of the active sites in a catalyst containing highly dispersed copper-oxo species on ceria during low-temperature CO oxidation using time-resolved X-ray absorption spectroscopy. We quantitatively demonstrate that the CO oxidation mechanism below 90 °C involves an oxygen intermediate strongly bound to the active sites as well as the redox activity of Cu2+/Cu+ and Ce4+/Ce3+ couples.

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25. Februar 2020
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Enhanced CH3OH selectivity in CO2 hydrogenation using Cu-based catalysts generated via SOMC from GaIII single-sites

Small and narrowly distributed nanoparticles of copper alloyed with gallium supported on silica containing residual GaIII sites can be obtained via surface organometallic chemistry. This material is highly active and selective for CO2 hydrogenation to CH3OH. In situ X-ray absorption spectroscopy shows that gallium is oxidized under reaction conditions while copper remains as Cu0.

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