The direct synthesis of hydrogen peroxide from molecular oxygen and hydrogen using gold and palladium based catalysts supported on titanium dioxide

Bayntun, Ben 2025. The direct synthesis of hydrogen peroxide from molecular oxygen and hydrogen using gold and palladium based catalysts supported on titanium dioxide. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The direct synthesis of hydrogen peroxide (H2O2) from molecular hydrogen and oxygen was investigated using palladium (Pd) and gold-palladium (AuPd) supported catalysts. The first part of the Thesis focused on the synthesis of monometallic Pd and bimetallic AuPd supported catalysts with a simple, industrially scalable wet impregnation procedure based on PdCl2 and HAuCl4 precursor compounds in the absence of excess chloride, the use of which has previously been commonplace. Catalysts were tested under optimised batch conditions and flow conditions more relevant for industrial application. It was found that, without the excess chloride, limited AuPd alloying was observed and the synergistic enhancement often reported in the literature was not observed, with catalytic activity correlating with Pd content. The catalysts still retained significant amounts of chloride (associated with the use of chloride-based metal precursors), which promoted particle agglomeration and activity loss under reaction conditions. This was particularly apparent under flow conditions, where leached Pd contaminated the walls of the reactor. In the final part of the thesis, chlorine-free catalyst formulations were investigated. Pd(OAc)2 based formulations were prepared via an acetone impregnation protocol, with the resulting materials comparing well with PdCl2 based analogues. The catalysts did not suffer from the same activity loss as the chloride-based catalysts upon reuse. The Pd nanoparticles contained an unusually high quantity of defect sites, but these sites did not correlate with H2O2 degradation activity, which may have been expected given earlier reports in the literature. Lastly, bimetallic catalyst formulations were investigated based on Pd(OAc)2 and Au(OAc)3. A clear AuPd synergistic effect was observed, with the bimetallic 0.5%Au-0.5%Pd/TiO2 catalyst (90 molH2O2 kgcat-1 h -1 ) significantly outperforming the monometallic 0.5%Pd/TiO2 analogue (33 molH2O2 kgcat-1 h -1 ). The bimetallic catalyst was found to consist of AuPd random alloy nanoparticles of 12 nm mean diameter which were thought to be responsible for the enhanced H2O2 synthesis activity. The preliminary testing of the chlorine-free catalyst formulations was promising and laid the foundations for future studies.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry
Date of First Compliant Deposit:	6 March 2026
Last Modified:	06 Mar 2026 09:14
URI:	https://orca.cardiff.ac.uk/id/eprint/185555

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