Reversible and Irreversible Cation Intercalation in NiFeO<sub><i>x</i></sub>Oxygen Evolution Catalysts in Alkaline Media
Hanna Trzesniowski, Nipon Deka, Onno van der Heijden, Ronny Golnak, Jie Xiao, Marc T. M. Koper, Robert Seidel, Rik V. Mom
Abstract
High Resolution Image Download MS PowerPoint Slide 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 Ni 0.8 Fe 0.2 O x 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 V RHE, 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.