In-situ environmental TEM studies of electro- and photo-electrochemical systems for water splitting

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Despite important developments in recent years, photo-electrochemical systems for water splitting and production of H2 that have been identified so far are still hampered either by conversion efficiency, the costs of noble metal catalysts or by corrosion stability in aqueous environments. Design of improved non-noble electro-catalysts and integration into stable photo-electrodes requires elucidating the mechanisms determining their activity and stability.The main goal of this proposed project is an improved fundamental understanding of the atomic and electronic structure of electro-catalysts for hydrogen- and oxygen-evolution during water splitting and improved strategies for integration into photocathodes and anodes in multi-junction semiconductor photo-electrochemical devices. Analytical and environmental Transmission Electron Microscopy (ETEM) with controlled in-situ electric and optical stimulation will be applied for studying structure and processes on different length scales from device level down to atomic scales. This gives access to the microstructure of the electrodes in the as prepared state, including catalyst particle size, morphology, surface coverage and interface properties to electrode buffer layers and semiconductors. Furthermore, the change of the atomic and electronic structure of the electro-catalysts in their active state during water splitting will be studied as well as processes leading to degradation and corrosion of the photo-electrochemical devices. We address three systems of high relevance within the SPP 1613, i.e. Si-based tandem and triple junctions as well as III-V compound photo-cathodes with different catalysts (Pt, Rh, MoS2) for hydrogen evolution. In addition, active states of Mn- and Co-oxide based electro-catalysts for oxygen evolution will be studied in-situ. Based on the improved understanding of processes which are induced by electrical and optical stimulation in H2O vapor, guidelines for development of improved electro-catalyst and their integration in photo-electro-chemical devices will be developed in close collaboration with the partner groups within the SPP.