• Trzesniowski, H.; Deka, N.; Van Der Heijden, O.; Golnak, R.; Xiao, J.; Koper, M.T.M.; Seidel, R.; Mom, R.V.: Reversible and Irreversible Cation Intercalation in NiFeOx Oxygen Evolution Catalysts in Alkaline Media. The Journal of Physical Chemistry Letters 14 (2023), p. 545-551

Open Access Version

For electrocatalysts with a layered structure, ion intercalation is a common phenomenon. Gaining reliable information about the intercalation of ions from the electrolyte is indispensable for a better understanding of the catalytic performance of these electrocatalysts. Here, we take a holistic approach for following intercalation processes by studying the dynamics of the catalyst, water molecules, and ions during intercalation using operando soft X-ray absorption spectroscopy (XAS). Sodium and oxygen K-edge and nickel L-edge spectra were used to investigate the Na+ intercalation in a Ni0.8Fe0.2Ox electrocatalyst during the oxygen evolution reaction (OER) in NaOH (0.1 M). The Na K-edge spectra show an irreversible intensity increase upon initial potential cycling and a reversible intensity increase at the intercalation potential, 1.45 VRHE, coinciding with an increase in the Ni oxidation state. Simultaneously, the O K-edge spectra show that the Na+ intercalation does not significantly impact the hydration of the catalyst.