Developing nanocomposite materials for catalytic applications

Abstract

In the field of nanoscale catalyst design, there are many parameters that must be carefully controlled to yield effective nanocomposite materials, such as physical properties, metal-support interactions, and experimental conditions. The development of reliable and accessible synthetic methods that can selectively and simultaneously modulate catalyst properties, such as through the local formation of interfaces, is integral to the continued development of advanced nanocatalysts.

The established sol-immobilisation method of preparing supported nanoparticles was extended to using metal-organic frameworks as a support, being employed to generate Pd/CuBTC nanoparticle-MOF composites. The possibilities of this method were further explored using water- and methanol-based sol-immobilisations, and an alternative CuTPA MOF support.

The limited stability of MOFs was exploited to reduce these NP-MOF composites into tailored nanocomposites, using a novel chemical-based method to generate PdCu/Cu2O nanomaterials, in contrast to conventional thermal treatments that proceed via MOF pyrolysis. Characterisation with XRD, XAFS and HRTEM determined that it is possible to induce local Pd Cu alloying within the Pd nanoparticles at room temperature, using an NaBH4 reducing agent and an amine-based protecting agent. Additionally, precise control of reduction temperature, reductant concentration, and protecting agent concentration was demonstrated to allow various properties of the generated nanocomposites to be finely tuned, including the alloying extent, particle size, and support oxidation state. Furthermore, the catalytic performance of both the Pd/CuBTC composites and PdCu/Cu2O nanocomposites was evaluated using the reduction of 4-nitrophenol and CO oxidation as model reactions, and the relative performances of the Pd and PdCu nanoparticles for both reactions are discussed.

The research presented in this thesis demonstrates new insight into the field of nanocomposite design via the development of a novel synthetic method, which has been demonstrated to generate alloyed nanoparticles and controlled nanocomposites under standard laboratory conditions.

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Identifiers

ORCID for Evan William Lynch: orcid.org/0009-0007-6799-7457

ORCID for Peter Wells: orcid.org/0000-0002-0859-9172

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