Single-atom Catalysis in Photocatalytic Investigations

In the light of environmental and energy supply crises, new technologies which can satisfy mankind's energy demand in a sustainable way must be developed. Heterogeneous photocatalysis is one of the most promising fields of research in this regard, as it allows to directly convert energy in sunlight to chemical bonds in molecules. The process is conceptually similar to the photosynthetic process in plants, but a semiconductor is used to absorb the light and catalyze the reactions. In reality, a so-called co-catalyst on the semiconductor surface is necessary for proper function, and this usually means depositing noble metal particles on the surface. Exactly how such nanoparticles work is usually elusive, and this makes the rational design and optimization of photocatalysts difficult. The high costs of the precious metal is also a major roadblock making the upscaling of a lab-scale photocatalyst economically unviable. If we can better understand the role of the co-catalyst, we can develop new strategies to reduce or even replace this material with more economical alternatives. In this proposal, we intend to apply the concept of single-atom catalysis to heterogeneous photocatalysis. Single noble metal atoms such as Platinum, Rhodium or Iridium will be deposited directly on semiconductor single crystal surfaces of Titanium dioxide and hematite (Iron oxide) with a precisely known structure. Highly sensitive surface science methods, including scanning probe microscopy as well as spectroscopic and spectrometric techniques, will be used to characterize the local structure of the active site, and relate it to the catalytic function. The project combines the expertise of the host group in the synthesis and characterization of single atoms on metal oxides, and the applicant’s practical knowledge of UHV photocatalysis, and will ultimately establish clear structure-performance relationships in order to facilitate the rational design of economically viable photocatalysts.