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Investigations of interaction between gold and palladium in alcohol oxidation reactions

Huang, Xiaoyang 2020. Investigations of interaction between gold and palladium in alcohol oxidation reactions. PhD Thesis, Cardiff University.
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Abstract

Synergistic interactions between Au and Pd in supported heterogeneous catalysts have long been attributed to the performance enhancements exhibited by AuPd bimetallic catalysts in the liquid phase oxidation of alcohols. However, conclusive experimental evidence for this synergy is somewhat limited and remains a subject of debate, which indirectly inhibits catalyst design. In this PhD thesis, a new explanation is provided for synergistic interactions between Au and Pd in supported AuPd bimetallic catalysts. The aqueous phase aerobic oxidation of 5-Hydroxymethylfurfural (HMF) was selected as a probe reaction for these studies, given the platform chemicals current significance within this field of research and the abundance of work documented on this reaction. It is proposed that the performance of either Au or Pd in AuPd bimetallic catalysts can be enhanced by facilitating the movement of electrons from one metallic component to the other, indicating that synergy is attributable to a redox co-operation between the two metals. This synergy is markedly enhanced when the two metals are not alloyed, which is demonstrated with spatially separated Au and Pd nanoparticles, noted as (Au + Pd)/C, and physical mixtures of the monometallic counterparts. This theory is evidenced through careful experimental design, utilizing both chemical and electrochemical measurements, e.g., cyclic voltammetry (CV), Short Circuit Current (SCC). Furthermore, it is also demonstrated that this phenomenon is independent of the reaction substrate; similar trends in catalytic performance were also observed for the aqueous phase aerobic oxidation of glycerol and ethanol. The catalysts used in this work were characterized by a number of different techniques, including: Scanning Transmission Electron Microscopy (STEM), Temperature Programmed Reduction (TPR), ultraviolet–visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), to further validate the proposed theory. It is considered that this discovery will provide a new approach to the design and synthesis of highly efficient bimetallic heterogeneous catalysts and contains potential applications in fuel cell research.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 20 January 2021
Last Modified: 21 Jan 2021 09:42
URI: http://orca.cardiff.ac.uk/id/eprint/137805

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