Tailored Au and Ru catalysts via modified sol co-precipitation for oxidation reactions

Mughal, Bushra 2026. Tailored Au and Ru catalysts via modified sol co-precipitation for oxidation reactions. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

In this thesis, supported Au and Ru catalysts have been synthesised by a modified sol co precipitation method for oxidation reactions with an aim to tune their interface chemistry. In this method, the prepared sols of Au and Ru were precipitated with titanium tetraisopropoxide (TTIP) as a precursor for TiOx in the colloidal phase, followed by subsequent immobilisation on the support material. This approach was expected to enhance the activity and stability of the metal nanoparticles. For comparison, the standard references of Au and Ru have been prepared using the colloidal sol-immobilisation method. Initially, the TiO2-P25 supported Au catalysts were studied for the CO oxidation reaction. The optimised Au-TTIP composite catalyst has demonstrated enhanced catalytic performance as compared to the standard Au/TiO2 reference. The key characterisations (AC-STEM and EELS) suggested that the optimised Au-TTIP composite catalyst lacks the complete encapsulation of Au into a TiOx overlayer, unlike the classical SMSI effect in the Au/TiO2 catalyst. However, the CO-DRIFTS studies suggested the fabrication of a unique Au-TiOx interface with additional Au sites for CO adsorption. The suppressed sintering upon high temperature calcination pre treatment suggested stronger interactions of the Au-TTIP composite with the support in comparison to the Au/TiO2. From these findings, it was concluded that the suppression of Au agglomeration via the localised TiOx sites in proximity to Au at the interface sites, while maintaining the high catalytic performance, could be achieved by keeping the balance between the fabricated Au-TiOx interfacial perimeter sites and exposed surface Au species in the catalyst. Later, the same preparation method was used to prepare Au-TTIP composites on a range of support materials with different properties to examine the versatility of the method and develop an understanding of the origin of enhanced catalytic performance. Similar catalytic enhancement for CO oxidation was observed by Au-TTIP on various supports (graphene nanoplatelets (GNP), CeO2, ɣ-Al2O3, and SiO2) as compared to the standard counterparts. The origin of high catalytic activity was suggested to be the fabricated Au-TiOx interface. Nonetheless, the true interfacial structure (modification via TTIP precipitation) is still unclear and would need a computational study combined with in situ HR-TEM for further understanding. In addition to Au, a similar preparation approach has been used to prepare a Ru-TTIP catalyst on TiO2-P25 support for total propane oxidation, to examine the versatility of the method on different metals and oxidation reactions. The modified Ru catalyst has demonstrated improved catalytic performance in comparison to the standard Ru reference. However, the enhancement was not as pronounced as that observed for the Au catalyst. A range of characterisation techniques has been used to study reaction induced changes by fresh and post-reaction sample analysis to correlate deactivation during stability tests.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry Schools > Physical, Chemical & Environmental Sciences
Date of First Compliant Deposit:	4 September 2026
Last Modified:	04 Sep 2026 11:08
URI:	https://orca.cardiff.ac.uk/id/eprint/189396

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