Garcia-Diez, R.; Wibowo, R. E.; Kataev, E.; Quevedo Garzon, W.; van der Merwe, M.; Duarte-Ruiz, D.; Cocchi, C.; Bär, M.: High-Valent Intermediate Observed in a Cu-Based OER Electrocatalyst by Operando X-ray Absorption Spectroscopy. The Journal of Physical Chemistry Letters 16 (2025), p. 6328-6333
10.1021/acs.jpclett.5c00944
Open Accesn Version
Abstract:
Understanding the chemical transformations governing the oxygen evolution reaction (OER) in Cu-based electrocatalysts is critical for advancing cost-efficient alkaline water-splitting technologies. In this study, we employ synchrotron-based operando Cu L3-edge X-ray absorption spectroscopy (XAS) and potentiodynamic techniques to probe the key intermediate species involved in alkaline OER. Our findings reveal that this metastable species exhibits an electronic structure resembling high-valent Cu complexes, particularly those associated with the CuO2– ion. Potentiodynamic measurements indicate that the high-valent intermediate emerges at potentials as low as 1.62 VRHE, coinciding with the oxidative process traditionally attributed to the Cu2+ ↔ Cu3+ redox transition, suggesting that the formation of the high-valent intermediate is directly linked to this redox process. This work provides valuable insights into the interplay between redox chemistry and catalytic performance in Cu-based OER electrocatalysts and provides further insights into the nature of the chemical species governing the oxygen evolution reaction mechanism.