Shedding Light on Active Site Reconstruction and Structural Transformation of Oxygen Evolution Reaction Catalysts for Water Electrolysis

Designing efficient and stable electrolcatalysts for the demanding oxygen evolution reaction (OER) in water electrolysis is challenging and we are still lacking fundamental understanding of the underlying processes related to catalyst transformations governing their final activity and stability. Only the combination of operando spectroscopy techniques with electrochemical measurements can promote a deeper understanding on the interplay of different phenomena taking place during OER [1]. In this work, we utilize operando techniques like X-ray Absorption Spectroscopy (XAS) and Surface Enhanced Raman Spectroscopy (SERS) [2], in combination with specifically designed electrochemical protocols to study i) the reconstruction/reactivation of active sites in Ir-based OER catalysts for acidic media (Fig. 1a-c) and Ni-based OER catalysts for alkaline media (Fig. 1d) and ii) the identification of the relevant OER active species which will eventually define the final electrocatalyst performance [3]. We show not only the formation of the active species for OER but also the dynamic operando transformation of the Ir- and Ni-based electrocatalysts before the onset of OER but also their structural transformation due to electro-oxidation during OER, processes that lead to the final active phase. The underlying mechanisms studied via our operando analysis provide fundamental understanding of reaction mechanism but also guidance for the design of efficient OER catalysts optimized for their operation in technical devices. References [1] Spanos I, Tesch MF, Yu M, Tüysüz H, Zhang J, Feng X, Müllen K, Schlögl R, Mechler AK: ACS Catal 2019, 9:8165-8170. [2] Lim A, Ham K, Tesch MF, Spanos I: to be submitted [3] Lim A, Ham K, Tesch MF, Spanos I:Current Opinion in Electrochemistry 2023, 39:101272 Figure 1