Probing surface species of electrocatalysts at atomic scale

Tong Li, ZGH and Ruhr-University Bochum, Bochum, Germany
Olga Kasian, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany

The topmost atomic layers of electrocatalysts determine mechanism and kinetics of the reactions and play a crucial role in many important industrial processes, e.g. water splitting for hydrogen generation, chlor-electrolysis, or carbon dioxide reduction. Optimizing the performance of electrocatalysts requires a detailed understanding of how species react during the catalytic process, and thus the surface state ideally at the atomic scale. Here, we combine atom probe tomography, electron microscopy and spectroscopy to reveal in a model study the three-dimensional, atomic scale surface structure of a thermally and electrochemically grown iridium-based oxides, efficient electrocatalysts for the oxygen evolution reaction. We discovered low stoichiometry Ir-O species on the surfaces of the three oxides, which correlate with their activity and stability. Additionally, electrochemical growth of oxides in deuterated solutions allowed us to detect a monolayer of hydroxy-groups in Ir-O which provides an additional explanation for enhanced activity of electrochemically formed oxides .

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