Designing and Testing Model Systems for Catalysis: monomers, dimers and clusters

The great challenge of the 21st century is to deliver cheap and green energy to the growing world population. Some sectors will be difficult to decarbonize by electrification and requires the use of chemicals. Hydrogen produced through acidic water splitting can be used as feedstock for chemical processes and as an energy carrier to alleviate the intermittency of renewables. In order for water splitting to become viable, alternative catalysts are needed. Furthermore, a better understanding of catalysis as a whole is needed to accelerate the discovery of new catalyst materials. This thesis explores catalytic model systems with low complexity to further our understanding and improve the methods used to explore new catalysts.
Benchmarking the hydrogen evolution reaction: Current experimental practices within the field of hydrogen evolution suffer from several pitfalls. Through the systematic analysis of a wide range of Pt catalyst loadings, mass transport limitations in the rotating disk electrode (RDE) setup are shown to be ubiquitous for acidic HER. The consequence is that the true catalyst activity of Pt is still unknown but is three orders of magnitude higher than earth abundant alternatives. A strategy of reduced catalyst loading is suggested to mitigate mass transport limitations in RDE and the best experimental practices are highlighted. 
Small entities for the hydrogen evolution reaction: Small entities i.e. monomers, dimers and trimers are existing new catalyst candidates. Dimers and trimers are especially difficult to synthesize chemically and literature reports on the subject are sparse within hydrogen evolution. By the use of a cluster source deposition technique Pt monomers and dimers were investigated for the hydrogen evolution reaction. The atomic structure of the deposited entities could not be confirmed, but the catalytic activity was found to be markedly worse than Pt nanoparticles.