Investigation of Heterogeneous Photocatalysts based on TiO2-Graphene Composites in Selective Synthetic Transformations

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Heterogeneous photocatalysis is an exciting technology. The development of catalysts that allow for exploiting light sources in the VIS range, e.g., sunlight, is of particular interest for numerous applications. Here we propose to develop, synthesize and characterize efficient photocatalytic TiO2-carbon nanomaterial-based composites and to rationalize their activity. The composites will be prepared exclusively ex situ via simple mixing of different commercially available, well-known and characterized TiO2 nanoparticles and commercially available graphene species. Each component is known as an important ingredient in heterogeneous photocatalysts. Next to exploring the behavior of the as prepared composites, the influence of subsequent hydrothermal methods or sintering will be explored. Structural and electronic behavior of the new materials will be analyzed in cooperation with Prof. Guido Grundmeier and Prof. Jörg Lindner. The composites will be investigated experimentally and theoretically in selective organic photoredox catalytic synthetic carbon-carbon bond forming transformations. Next to quantum efficiency and catalytic activity it will be also determined whether a reaction occurs on the surface of TiO2 or the graphene species and if this is influencing product selectivities. The in-depth understanding of the photocatalytic properties of the composite materials will be a particular focus of our work: First-principles total-energy and electronic-structure calculations based on density-functional theory will be performed in order to explore the structure and catalytic properties of model systems selected in correspondence to the synthesized material. Transmission electron microscopy and X-ray diffraction data are used to ensure that the simulated models match closely the structural motifs that occur in the synthesized structures. Calculations beyond ground-state DFT, i.e., constrained DFT, time-dependent DFT, and many-body perturbation theory will be used to address the excited states relevant for the photocatalysis. The calculations will not only be used to rationalize the experimental findings but will assist the design of efficient new catalysts.