Development of New Precursors and Processes for the Controlled Deposition of Platinum Groups Metals

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The platinum group metals (PGM: Ru, Rh, Pd, Os, Ir and Pt), which can be applied in molecular form (homogeneous catalysis) or as nanostructured materials (heterogeneous catalysis), find widespread application as highly efficient and effective catalysts in chemical synthesis of organic compounds or in fuel cell applications. Due to their low abundance and challenging mining, recent research often focusses on PGM-free alternatives with comparable catalytic activity, more efficient utilization or environmentally friendly recycling strategies. The current proposal shall contribute to a more efficient preparation of nanostructured heterogeneous PGM catalysts via chemical vapor deposition (CVD), by understanding the underlying chemical and physical mechanisms. The CVD method allows to achieve solvent-free, stable and homogeneous deposition of materials even inside of open-porous substrates, which is essential for efficient catalyst materials. Therefore, the availability, understanding and control over defined molecular precursors with high volatility and matching reactivity profile is essential for a targeted deposition via the gas phase. The chemical and physical properties of new PGM precursor libraries will be compared with existing precursors, to establish molecular structure-property relations of reactivity and volatility, respectively. Besides precursor chemistry, a target-oriented materials synthesis using a matching deposition strategy for each precursor is crucial for in-depth analysis of underlying reaction pathways. Only a comprehensive understanding and control of material processing, yields defined catalytically active surfaces, which in itself forms the foundation of materials-oriented structure-property relations for the catalytic activity in fuel cell applications, for example. In particular, in-situ and in-operando characterization methods (i.e. IR spectroscopic analysis of gaseous PGM precursors or mass spectrometric characterization of air-borne decomposition products in CVD systems) unlock further insights under realistic reaction conditions. This project follows the holistic approach "from molecules to materials", which is underlined by structuring the research efforts in two intertwined research foci - one precursor chemistry and the other materials science centered. This integrated approach is considered necessary to assess the precursor influence on the technological application of the resulting materials as heterogeneous catalysts and addressing the technological relevance as a long-term objective. The findings on the molecular and materials chemistry of PGM precursors and catalyst materials will be further corroborated by collaborations with external research groups contributing with theoretical molecular and materials modelling and application centered fuel cell research.