Towards improved catalyst design via realistic modelling and atomistic simulations

Abstract

Heterogeneous catalysts are used in a huge number of applications across many industries. Determining how each of a multitude of factors influence catalytic activity is a complex and difficult task, but is necessary if new, improved catalysts are to be developed. While much of this work is applicable to heterogeneous catalysis in general, the oxygen reduction reaction (ORR) that takes place in hydrogen fuel cells has been a central theme.
This thesis describes how computational studies can be used to build on our understanding of such catalysts, focusing on the effects of nanoparticle morphology, alloying and those of the support. In order to capture these effects, ever more realistic simulations must be performed.
We compare real platinum nanoparticle structures from microscopy experiments with simulated models, and find that the richness of morphologies seen in the real nanoparticles is important for activity. A method to build comparable structures via annealing is also described. For cobalt platinum alloyed nanoparticles, which are relevant to the ORR, a direct comparison of structures is much more challenging. We have compared measurements of structural strain between theory and experiment in order to help determine the cobalt distribution within such nanoparticles, which remains an important and unresolved question, and is particularly important for alloyed nanoparticle stability. Finally, the effects of both titania and alumina supports are shown to be significant for ligand adsorption, and models should include them where possible. Titania is shown to reduce the binding strength of oxygen and carbon monoxide when used as a support for platinum nanoparticles.
These studies represent different steps in the direction of realistic simulations, where more factors are accounted for than in current routine calculations. The goal of any simulation is to capture all the important details of a real system in order to better reproduce the results, and ultimately make consistent and accurate predictions. Such simulations would be invaluable to catalyst design, reducing the reliance on expensive trials of real systems.

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Identifiers

ORCID for Chris-Kriton Skylaris: orcid.org/0000-0003-0258-3433

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