B03

Data contribution (Project B03, Prof. Gerd Bacher)

We investigate the dynamic behaviour of Co-based catalysts during the (pre-)oxygen evolution reaction (OER) using operando UV–Vis spectroelectrochemical measurements. This technique allows us to monitor changes in the electronic transitions of the catalyst under different electrochemical conditions, such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry (CA). It provides a direct correlation between optical signatures and electrochemical response, enabling the tracking of cobalt oxidation state changes, in particular the evolution of Co³⁺ d–d transitions over time. Using this method, it is possible to gain information about both the Co²⁺ → Co³⁺ oxidation process and the formation of an oxyhydroxide surface layer in the pre-OER region.

Thus, we contribute operando spectroelectrochemical datasets, which include:

• Steady-state or time-resolved UV–Vis absorption spectra recorded under applied electrochemical control
• Corresponding current–potential data obtained from electrochemical measurements (e.g. LSV, CV, or CA)

Currently, we are working with Co₃O₄ and V-doped Co₃O₄ nanoparticles provided by C03 (Hatem Amin) and collaborating with A09 (Sheila Hernández) to complement the UV–Vis results with in-situ Raman spectroscopy. Combining these two operando techniques allows us to obtain both electronic and structural information from the same materials under reaction conditions. The integration of these datasets contributes to a deeper understanding of how cobalt oxide catalysts transform during the OER and how their surface structure and oxidation states evolve over time.