Resolving the effect of oxygen vacancies on Co nanostructures using soft XAS/X-PEEM

Qiu, Chengwu, Odarchenko, Yaroslav, Meng, Qingwei, Xu, Shaojun, Lezcano-Gonzalez, Ines, Olalde-Velasco, Paul, Maccherozzi, Francesco, Zanetti-Domingues, Laura, Martin-Fernandez, Marisa and Beale, Andrew M. 2022. Resolving the effect of oxygen vacancies on Co nanostructures using soft XAS/X-PEEM. ACS Catalysis 12 (15) , 9125–9134. 10.1021/acscatal.2c00611

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Abstract

Improving both the extent of metallic Co nanoparticle (Co NP) formation and their stability is necessary to ensure good catalytic performance, particularly for Fischer–Tropsch synthesis (FTS). Here, we observe how the presence of surface oxygen vacancies (Ovac) on TiO2 can readily reduce individual Co3O4 NPs directly into CoO/Co0 in the freshly prepared sample by using a combination of X-ray photoemission electron microscopy (X-PEEM) coupled with soft X-ray absorption spectroscopy. The Ovac are particularly good at reducing the edge of the NPs as opposed to their center, leading to smaller particles being more reduced than larger ones. We then show how further reduction (and Ovac consumption) is achieved during heating in H2/syngas (H2 + CO) and reveal that Ovac also prevents total reoxidation of Co NPs in syngas, particularly the smallest (∼8 nm) particles, thus maintaining the presence of metallic Co, potentially improving catalyst performance.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Publisher:	American Chemical Society
ISSN:	2155-5435
Funders:	EPSRC
Date of First Compliant Deposit:	30 August 2022
Date of Acceptance:	14 July 2022
Last Modified:	04 May 2023 21:29
URI:	https://orca.cardiff.ac.uk/id/eprint/152227

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