Atomic Ordering-Induced Ensemble Variation in Alloys Governs Electrocatalyst On/Off States.

The catalytic behavior of a material is influenced by ensembles─the geometric configuration of atoms on the surface. In conventional material systems, ensemble effects and the electronic structure are coupled because these strategies focus on varying the material composition, making it difficult to understand the role of ensembles in isolation. This study introduces a methodology that separates geometric effects from the electronic structure.

Electrochemical Cell for Grazing-Incidence X-ray Absorption Spectroscopic Studies of Low-Loaded Electrodes.

X-ray absorption spectroscopy (XAS) is a powerful technique that provides information about the electronic and local geometric structural properties of newly developed electrocatalysts, especially when it is performed under operating conditions (i.e., ).

Photocatalytic dihydroxylation of light olefins to glycols by water.

Aliphatic diols such as ethylene and propylene glycol are the key products in the chemical industry for manufacturing polymers. The synthesis of these molecules usually implies sequential processes, including epoxidation of olefins using hydrogen peroxide or oxygen with subsequent hydrolysis to glycols. Direct hydroxylation of olefins by cheap and green oxidants is an economically attractive and environmentally friendly route for the synthesis of diols.

Influence of strong π-acceptor ligands on Cr-K-edge X-ray absorption spectral signatures and consequences for the interpretation of surface sites in the Phillips catalyst.

X-ray absorption spectroscopy (XAS) has been central to the study of the Phillips polymerization catalyst (CrO/SiO). As Cr K-edge XAS signatures are sensitive to the oxidation state, geometry and types of ligands on surface (active) sites, the superposition of these effects makes their interpretation challenging. Notably, CO has been particularly used as a reductant to generate low valent Cr sites from CrO/SiO and as a structural IR probe for analysing reduced Cr surface sites.

X-ray Spectroscopy at the SuperXAS and Debye Beamlines: from in situ to Operando.

Understanding structure-performance relationships are essential for the rational design of new functional materials or in the further optimization of (catalytic) processes. Due to the high penetration depth of the radiation used, synchrotron-based hard X-ray techniques (with energy > 4.5 keV) allow the study of materials under realistic conditions (in situ and operando) and thus play an important role in uncovering structure-performance relationships.

Understanding the Reducibility of CeO Surfaces by Proton-Electron Transfer from CpCr(CO)H.

CeO is a popular material in heterogeneous catalysis, molecular sensors, and electronics and owes many of its special properties to the redox activity of Ce, present as both Ce and Ce. However, the reduction of CeO with H (thought to occur through proton-electron transfer (PET) giving Ce and new OH bonds) is poorly understood due to the high reduction temperatures necessary and the ill-defined nature of the hydrogen atom sources typically used. We have previously shown that transition-metal hydrides with weak M-H bonds react with reducible metal oxides at room temperature by PET.

In Situ X-ray Absorption Spectroscopy of LaFeO and LaFeO/LaNiO Thin Films in the Electrocatalytic Oxygen Evolution Reaction.

We study the electrocatalytic oxygen evolution reaction using in situ X-ray absorption spectroscopy (XAS) to track the dynamics of the valence state and the covalence of the metal ions of LaFeO and LaFeO/LaNiO thin films. The active materials are 8 unit cells grown epitaxially on 100 nm conductive LaSrMnO layers using pulsed laser deposition (PLD). The perovskite layers are supported on monolayer CaNbO nanosheet-buffered 100 nm SiN membranes.

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

The reversible phase transitions in phase-change memory devices can switch on the order of nanoseconds, suggesting a close structural resemblance between the amorphous and crystalline phases. Despite this, the link between crystalline and amorphous tellurides is not fully understood nor quantified. 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.

Machine Learning for Quantitative Structural Information from Infrared Spectra: The Case of Palladium Hydride.

Infrared spectroscopy (IR) is a widely used technique enabling to identify specific functional groups in the molecule of interest based on their characteristic vibrational modes or the presence of a specific adsorption site based on the characteristic vibrational mode of an adsorbed probe molecule. The interpretation of an IR spectrum is generally carried out within a fingerprint paradigm by comparing the observed spectral features with the features of known references or theoretical calculations. This work demonstrates a method for extracting quantitative structural information beyond this approach by application of machine learning (ML) algorithms.

Active Sites in Cr(III)-Based Ethylene Polymerization Catalysts from Machine-Learning-Supported XAS and EPR Spectroscopy.

The ethylene polymerization Phillips catalyst has been employed for decades and is central to the polymer industry. While Cr(III) alkyl species are proposed to be the propagating sites, there is so far no direct experimental evidence for such proposal. In this work, by coupling Surface organometallic chemistry, EPR spectroscopy, and machine learning-supported XAS studies, we have studied the electronic structure of well-defined silica-supported Cr(III) alkyls and identified the presence of several surface species in high and low-spin states, associated with different coordination environments.

MICROCIRCULATORY ALTERATIONS IN STABLE CORONARY ARTERY DISEASE PATIENTS WITH CONCOMITANT COVID-19.

Objective: The aim: To evaluate the alterations in microcirculation of stable coronary artery disease (SCAD) patients with concomitant COVID-19.

Patients And Methods: Materials and methods: The cross-sectional study analyzed the data from 80 patients, being subdivided as follows: group 1 (G1) - SCAD without COVID-19 (n=30); group 2 (G2) - SCAD with concomitant COVID-19 (n=25); group 3 (G3) - COVID-19 without SCAD (n=25). The control group included 30 relatively healthy volunteers.

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.

INTRACARDIAC HEMODYNAMICS, CEREBRAL BLOOD FLOW AND MICROEMBOLIC SIGNAL BURDEN IN STABLE CORONARY ARTERY DISEASE PATIENTS WITH CONCOMITANT COVID-19.

Objective: The aim: To estimate the changes in intracardiac hemodynamics, cerebral blood flow (CBF), and microembolic signals` (MES) burden in stable coronary artery disease (SCAD) patients with concomitant COVID-19.

Patients And Methods: Materials and methods: The cross-sectional study analyzed the data from 80 patients, being subdivided as follows: group 1 (G1) - SCAD without COVID-19 (n=30); group 2 (G2) - SCAD with concomitant COVID-19 (n=25); group 3 (G3) - COVID-19 without SCAD (n=25). The control group (CG) included 30 relatively healthy volunteers.

Confined Ru Sites in a 13X Zeolite for Ultrahigh H Production from NH Decomposition.

Catalytic NH synthesis and decomposition offer a new promising way to store and transport renewable energy in the form of NH from remote or offshore sites to industrial plants. To use NH as a hydrogen carrier, it is important to understand the catalytic functionality of NH decomposition reactions at an atomic level. Here, we report for the first time that Ru species confined in a 13X zeolite cavity display the highest specific catalytic activity of over 4000 h for the NH decomposition with a lower activation barrier, compared to most reported catalytic materials in the literature.

Surface Redox Dynamics in Gold-Zinc CO Hydrogenation Catalysts.

Au-Zn catalysts have previously been shown to promote the hydrogenation of CO to methanol, but their active state is poorly understood. Here, silica-supported bimetallic Au-Zn alloys, prepared by surface organometallic chemistry (SOMC), are shown to be proficient catalysts for hydrogenation of CO to methanol. X-ray absorption spectroscopy (XAS), in conjunction with gas-switching experiments, is used to amplify subtle changes occurring at the surface of this tailored catalyst during reaction.

Active Site Descriptors from Mo NMR Signatures of Silica-Supported Mo-Based Olefin Metathesis Catalysts.

The olefin metathesis activity of silica-supported molybdenum oxides depends strongly on metal loading and preparation conditions, indicating that the nature and/or amounts of the active sites vary across compositionally similar catalysts. This is illustrated by comparing Mo-based (pre)catalysts prepared by impregnation (2.5-15.

Reaction-Induced Formation of Stable Mononuclear Cu(I)Cl Species on Carbon for Low-Footprint Vinyl Chloride Production.

Copper catalysts are attractive candidates for Hg-free vinyl chloride monomer (VCM) production via acetylene hydrochlorination due to their non-toxic nature and high stability. However, the optimal architecture for Cu-based catalysts at the nanoscale is not yet fully understood. To address this gap, the metal precursor and the annealing temperature are modified to prepare copper nanoparticles or single atoms, either in chlorinated or ligand-free form, on an unmodified carbon support.

Origin of the Activity Trend in the Oxidative Dehydrogenation of Ethanol over VO /CeO.

Supported vanadia (VO ) is a versatile catalyst for various redox processes where ceria-supported VO have shown to be particularly active in the oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano-shaped ethanol ODH activity trend for VO /CeO catalysts using operando quick V K- and Ce L - edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH.

Direct Photocatalytic Synthesis of Acetic Acid from Methane and CO at Ambient Temperature Using Water as Oxidant.

Direct functionalization of methane selectively to value-added chemicals is still one of the main challenges in modern science. Acetic acid is an important industrial chemical produced nowadays by expensive and environmentally unfriendly carbonylation of methanol using homogeneous catalysts. Here, we report a new photocatalytic reaction route to synthesize acetic acid from CH and CO at room temperature using water as the sole external oxygen source.

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 identified that the concentration of Fe species in the working state-of-the-art Pt-FeO catalysts quantitatively correlates to their preferential carbon monoxide oxidation steady-state reaction rate at ambient temperature. Deactivation of such catalysts with time on stream originates from irreversible oxidation of active Fe sites. The active Fe species are presumably Fe O clusters in contact with platinum nanoparticles; they coexist with spectator trivalent oxidic iron (Fe ) and metallic iron (Fe ) partially alloyed with platinum.

Assessing the environmental benefit of palladium-based single-atom heterogeneous catalysts for Sonogashira coupling.

The Pd-Cu catalysed Sonogashira coupling of terminal alkynes and aryl halides is a cornerstone synthetic strategy for C-C bond formation. Homogeneous organometallic systems conventionally applied are typically not reusable and require efficient downstream Pd removal steps for product purification, making it challenging to fully recover the precious metal. A holistic cradle-to-gate life cycle assessment (LCA) unveils that process footprint can be improved up to two orders of magnitude from repeated catalyst reuse.

BCC-Cu nanoparticles: from a transient to a stable allotrope by tuning size and reaction conditions.

Metallic copper generally adopts an FCC structure. In this work, we detect highly unusual BCC-structured Cu nanoparticles as a transient intermediate during the H reduction of a Cu precursor, [CuOBu], grafted onto the surface of partially dehydroxylated silica. The Cu BCC structure, assigned by Cu K-edge XANES and EXAFS, as well as synchrotron PXRD, converts upon heating into the most commonly found FCC allotrope.

Flame-made ternary Pd-InO-ZrO catalyst with enhanced oxygen vacancy generation for CO hydrogenation to methanol.

Palladium promotion and deposition on monoclinic zirconia are effective strategies to boost the performance of bulk InO in CO-to-methanol and could unlock superior reactivity if well integrated into a single catalytic system. However, harnessing synergic effects of the individual components is crucial and very challenging as it requires precise control over their assembly. Herein, we present ternary Pd-InO-ZrO catalysts prepared by flame spray pyrolysis (FSP) with remarkable methanol productivity and improved metal utilization, surpassing their binary counterparts.

Beware of beam damage under reaction conditions: X-ray induced photochemical reduction of supported VO catalysts during XAS experiments.

X-ray absorption spectroscopy (XAS) is a powerful technique for the investigation of heterogeneous catalysts and electrocatalysts. The obtained XAS spectra are usually interpreted from the point of view of the investigated chemical processes, thereby sometimes omitting the fact that intense X-ray irradiation may induce additional transformations in metal speciation and, thus, in the corresponding XAS spectra. In this work, we report on X-ray induced photochemical reduction of vanadium in supported vanadia (VO) catalysts under reaction conditions, detected at a synchrotron beamline.

Correction to "Silica-Supported PdGa Nanoparticles: Metal Synergy for Highly Active and Selective CO-to-CHOH Hydrogenation".

[This corrects the article DOI: 10.1021/jacsau.1c00021.