Joshua Sims will defend his PhD thesis in Chemistry, supervised by Carine Michel, on 17 July 2025 at 14:00.

Thesis abstract

Biomass is a key ingredient to tackling the challenges of limited ressources, now and in the coming years. This has led to the development of the field of biomass conversion and upgrade in chemistry and in particular in catalysis. Contrary to catalysis in the petrochemical industry, biomass conversion reactions typically occur at the solid-water interface and not the solid-gas interface. This leads to new and exciting scientific challenges as new catalysts are designed that can operate in aqueous conditions while avoiding deactivation. This thesis investigates a key catalyst: Ru clusters supported over titania. In particular it addresses key challenges in the modelling of supported clusters catalysts, namely accounting for morphological diversity of Ru clusters as well as investigating the surface state of the catalyst in water. Important results include evidence that O-vacancies in the support affect the stability and morphology of supported Ru clusters, the existence of morphologies near the global minimum that feature under coordinated Ru atoms available for catalysis as well as evidence for water splitting into H + OH on the Ru clusters, indicating the existence of OH particles expected to be key players in some reaction mechanisms as well as catalyst deactivation. Along the way this thesis addresses challenges of optimising complex systems, developing a global optimisation strategy and employing machine learning to accelerate sampling.