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Work on 5D chemical imaging of an operating catalyst published

You can see the latest work from our former PhD student Dr Dorota Matras and our scientists on 5D chemical imaging in a new paper published at the Journal of Materials Chemistry A of the Royal Society of Chemistry (RSC): “Multi-length Scale 5D Diffraction Imaging of Ni-Pd/CeO2-ZrO2/Al2O3 Catalyst during Partial Oxidation of Methane.
The work was performed at ESRF in collaboration with UCL Chemistry, VITO and Boreskov Institute of Catalysis.

A 5D diffraction imaging experiment (with 3D spatial, 1D time/imposed operating conditions and 1D scattering signal) was performed with a Ni-Pd/CeO2-ZrO2/Al2O3 catalyst. The catalyst was investigated during both activation and partial oxidation of methane (POX). The spatio-temporal resolved diffraction data allowed us to obtain unprecedented insight into the behaviour and fate of the various metal and metal oxide species and how this is affected by the heterogeneity across catalyst particles. We show firstly, how Pd promotion although facilitating Ni reduction, over time leads to formation of unstable Ni-Pd metallic alloy, rendering the impact of Pd beyond the initial reduction less important. Furthermore, in the core of the particles, where the metallic Ni is primarily supported on Al2O3, poor resistance towards coke deposition was observed. We identified that this preceded via the formation of an active yet metastable interstitial solid solution of Ni-C and led to the exclusive formation of graphitic carbon, the only polymorph of coke observed. In contrast, at the outermost part of the catalyst particle, where Ni is predominantly supported on CeO2-ZrO2, the graphite formation was mitigated but sintering of Ni crystallites was more severe.

Read the full article at https://doi.org/10.1039/D1TA01464A.

 

Our latest work on X-ray tomographic diffraction imaging of operating dense ceramic hollow-fibre catalytic membrane reactors (CMRs)

You can see our latest work on X-ray tomographic diffraction imaging of operating dense ceramic hollow-fibre catalytic membrane reactors (CMRs) – “Real-time tomographic diffraction imaging of catalytic membrane reactors for the oxidative coupling of methane” in Catalysis Today. The paper is a result of a collaboration between scientists at UCL Chemistry, Finden, ESRF,  VITO and ISIS Neutron and Muon Source.

Real time tomographic diffraction figHighlights include:
  • Synchrotron X-ray diffraction computed tomography applied to three packed bed catalytic membrane reactors.
  • The solid-state evolution of catalysts and membranes is tracked under operating conditions.
  • A new crystal structure model of BaCo0.4Fe0.4Zr0.2O3-δ (BCFZ) is suggested and used for the diffraction data analysis

 

 

Catalytic membrane reactors have the potential to render the process of oxidative coupling of methane economically viable. Here, the results from operando XRD-CT studies of three different catalytic membrane reactors, employing BaCo0.4Fe0.4Zr0.2O3-δ (BCFZ) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite membranes with Mn-Na-W/SiO2 and La-promoted Mn-Na-W/SiO2 catalysts, are presented. It is shown that synchrotron X-ray tomographic diffraction imaging allows the extraction of spatially-resolved diffraction information from the interior of these working catalytic membrane reactors and makes it possible to capture the evolving solid-state chemistry of their components under various operating conditions (i.e. temperature and chemical environment).

Read the paper at https://doi.org/10.1016/j.cattod.2020.05.045

Our paper on the first region-of-interest high resolution X-ray diffraction computed tomography experiment of a Si-graphite electrode used for Li-ion battery applications has been published in Nano Letters

Our scientists’ new work on Si-graphite electrodes used for Li-ion battery applications with high resolution in situ X-ray chemical imaging has been published in a new paper, “Spatially Resolving Lithiation in Silicon–Graphite Composite Electrodes via in Situ High-Energy X-ray Diffraction Computed Tomography” in Nano Letters. The work was performed with Donal Finegan from the National Renewable Energy Laboratory and in collaboration with a team from the Electrochemical Innovation Lab (EIL) from UCL Chemical Engineering using ESRF’s ID15A beamline.

Optimizing the chemical and morphological parameters of lithium-ion (Li-ion) electrodes is extremely challenging, due in part to the absence of techniques to construct spatial and temporal descriptions of chemical and morphological heterogeneities. In this work, we present the first demonstration of combined high-speed X-ray diffraction (XRD) and XRD computed tomography (XRD-CT) to probe, in 3D, crystallographic heterogeneities within Li-ion electrodes with a spatial resolution of 1 μm. The local charge-transfer mechanism within and between individual particles was investigated in a silicon(Si)−graphite composite electrode. High-speed XRD revealed charge balancing kinetics between the graphite and Si during the minutes following the transition from operation to open circuit. Subparticle lithiation heterogeneities in both Si and graphite were observed using XRD-CT, where the core and shell structures were segmented, and their respective diffraction patterns were characterized.

Battery diagram

Figure: (a) XRD-CT slice taken at the beginning of the charge step showing a phase-distribution map of LiC12 (red), crystalline Si (green), and lithium silicides LixSi (blue). According to additive colour mixing, the colour teal represents a mixture of green (Si) and blue (lithiated Si). (b) Magnified regions of interest showing large particles of LixSi phase with crystalline Si cores (1-3) and smaller LixSi particles (4) interspersed in the graphite matrix. The yellow arrow highlights what looks to be evidence of delamination from a crystalline Si core.

Read more about it at https://www.esrf.eu/home/news/spotlight/content-news/spotlight/spotlight346.html

Read the article at https://pubs.acs.org/doi/full/10.1021/acs.nanolett.9b00955

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