Elucidating the role of catalyst-support interaction on the activity and stability of water splitting catalysts

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This proposal explores the nature and impact of chemical interactions between a catalyst and a solid support at electrified solid-liquid interfaces. Catalyst|support systems addressed here comprise non-precious metal catalysts as active sites for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The project will systematically study catalyst-support interactions using selected supports relevant to photoelectrochemical devices and establish relations between the geometric and electronic structure of the buried catalyst-support interface and its resulting photoelectrochemical activity and stability at the electrode-electrolyte interface.In order to reach this goal, a main focus is directed to understand the extent of electronic and structural interaction for different types of catalyst|support systems on a fundamental level. For instance, adsorptive interaction versus covalently attached active site interaction (via different linkage groups) will allow conclusions as to what extent the additional steps of functionalization and linkage are indeed required to obtain an active and stable catalyst|support system.As catalysts NiFe-based oxides and (oxy)hydroxides (NiFeOx) are investigated for the OER and catalysts with molecular MeN4 centers for the HER. Based on standard structural and electrochemical characterization different systems will be selected for a more detailed characterization.As advanced characterization techniques different methods are applied in-situ and operando as X-ray absorption spectroscopy (XAS) and Mössbauer spectroscopy. The stepwise analysis of the interface with respect to the presence of different gas atmospheres and electrolytes in combination with (ambient pressure) X-ray photoelectron spectroscopy (XPS) of selected samples will enable conclusions to what extent the electronic and structural interaction of the catalyst|support system are changed.While the main focus is directed on the catalyst|support interaction on model electrodes, the interdependence in real devices will be addressed as well. Therefore, the most promising catalyst systems will be investigated on the related semiconductors (SC) or SC + passivation layer. Thus, in contrast to the model electrode with one solid-solid interface, these devices combine all the interfaces and related interdependence.As a consequence, the acquired results should enable useful predictions for future works on a knowledge-based design of such functional composite structures that need to be integrated in devices within the follow-up project. While this project focusses on the fundamental aspects (but in close relation to relevant supports), in future work also the further optimization of catalysts or application of new catalytic systems will be addressed.The results obtained in this project might be of importance also for other catalytic systems or structures that uses strong electronic coupling for coordination of functional units.