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Revealing metal-support interactions at the nanoscale in Co/TiO2 catalysts by spatially resolved microscopy/spectroscopy

Qiu, Chengwu; (2022) Revealing metal-support interactions at the nanoscale in Co/TiO2 catalysts by spatially resolved microscopy/spectroscopy. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Fischer-Tropsch synthesis (FTS), involves the hydrogenation of CO under high pressure and is an alternative process to refining to produce fuels and fine chemicals. Industrially it is carried out using oxide-supported cobalt nanoparticles (CoNPs). The interaction between the CoNPs and the support can have a big influence on catalyst performance, affecting the availability of active surfaces, the stability of the nanoparticles and/or their electronic state. Here I use spatially resolved spectroscopy/microscopy to better understand the metal support interactions in Co/Rutile model systems possessing a range of Co nanoparticle sizes (6~24 nm). In chapter 3 I observe that CoNPs spread on the surface of rutile adopting a fried-egg-like shape after reduction in H2, which increases not only the amount of surface cobalt, but also the interaction between metal and support leading to the formation of non reducible cobalt titanate (inactive for FTS). In chapter 4 I find that the initial Co3O4 nanoparticles can be directly reduced to CoO/Co0 as a result of plasma treatment generating oxygen vacancies (Ovac) on the rutile surface. In chapter 5 I observe that dissociation of CO occurs on nanoparticles (≥ 15 nm) and that the Ovac surrounding these particles is consumed. Nanoparticles smaller than this are unaffected, except in the presence of both CO and H2 when small NPs (≤ 12 nm) (re)oxidise. In chapter 6, reduced TiO2-x is observed to appear at the periphery of CoNPs after H2 reduction. Surfactant coverings can inhibit TiO2 reduction and stop CoNPs aggregation, with FTS reactivity enhanced in this catalyst. In summary, this nano-spectroscopic study of these samples allowed us to better understand the influence of the cobalt-rutile interface on the evolving properties of the cobalt nanoparticles under various gas atmospheres. It is hoped that this can enable a better understanding of their influence on FTS performance.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Revealing metal-support interactions at the nanoscale in Co/TiO2 catalysts by spatially resolved microscopy/spectroscopy
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10141996
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