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Disputation Chiara Pasquini

24.05.2022 | 16:00
Thema der Dissertation:
The mechanism of the water oxidation reaction catalyzed by an amorphous Co-based catalyst is revealed using operando Raman and time-resolved X-ray absorption spectroscopy
Abstract: Hydrogen produced from water via electrolysis is the most promising carbon-free fuel at our disposal, it is considered one of the pillar for the decarbonization of our society. One of the bottleneck for a wider application of this technology is the efficiency of the water oxidation reaction, thus, a lot of effort has been directed in the investigation of catalysts and reaction mechanisms. The amorphous Co oxide catalyst (CoCat) is particularly active at neutral pH for the water oxidation reaction. In this thesis, the reaction mechanism for CoCat is studied by simultaneous coupling of electrochemistry with spectroscopic techniques. Operando X-ray absorption spectroscopy is adapted and employed to obtain time-resolved information on oxidation state changes and detailed insights on the reaction mechanism. Operando Raman spectra are collected at various applied potentials and show spectral changes, which can be assigned to two distinct Co oxidation reactions, establishing Raman spectroscopy as a novel tool to study metal oxidation states. Furthermore, Raman spectroscopy reveals the presence of local acidification at the catalyst surface due to proton transfer limitations, which strongly affects catalyst performances. The reaction mechanism differs in alkaline electrolytes, where the catalytic efficiency is higher. The differences between the two pH regimes are investigated to unravel the key factors for catalyst efficiency.

Zeit & Ort

24.05.2022 | 16:00

Raum 1.1.16
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)