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Disputation Gregor Zwaschka

25.11.2020 | 11:00
Titel der Dissertation:
Shining New Light on Water Electrolysis: Probing Electrolytic Water Splitting on Au and Pt with Micron Spatial and Femtosecond Temporal Resolution
Abstract: For a greenhouse gas emission free society, hydrogen from water electrolysis is fundamental. Despite decades of study, the mechanism of the cathodic half-cell reaction of water electrolysis, the hydrogen evolution reaction (HER), on the best available catalyst, Pt, remains controversial. At least in part, understanding is complicated by not being able to disentangle the involved timescales ranging from femtoseconds (interfacial charge transfer) to milliseconds (mass transport). I approach this problem by performing perturbation experiments with ultrashort laserpulses that drive the HER close to its reversible potential and induce charge transfer along the Pt-H bond. I disentangle the involved timescales by performing both i) time averaging electrochemical measurements under femtosecond laser irradiation and ii) time resolved sum frequency generation spectroscopy of Pt-H after laser excitation. Implications for the HER, our understanding of charge transfer at the solid/liquid interface and the behavior of H adsorbed on Pt electrodes is discussed. This work is extended to surfaces more closely related to industrial catalysts by investigating the anodic half-cell reaction of water electrolysis, the oxygen evolution reaction (OER) on polycrystalline gold samples by second harmonic microscopy. Surface chemistry such as oxidation/reduction, surface reconstruction and the OER are found to be highly local. Implications for the design of novel OER catalysts are discussed.

Zeit & Ort

25.11.2020 | 11:00