<i>Operando</i> Observation of the Electrochemical Oxygen Evolution Reaction with a Co Oxide Catalyst Using Fluorescence-yield Wavelength-Dispersive Soft X-ray Absorption Spectroscopy

Abstract

Herein, an electrochemical oxygen evolution reaction (OER) at the solid–liquid interface was investigated in real time using fluorescence-yield X-ray absorption spectroscopy (XAS) in the soft X-ray region, which is a newly developed technique. A dedicated electrochemical cell was used, and the OER on the surface of a Co/Pt thin film working electrode in an alkaline solution (NaOH, 0.1 M) was investigated. When the electrode potential was shifted to a positive value, the peak of the oxygen K-edge was successfully detected using this technique, and the peak intensity increased in correlation with the electrode potential. In addition, it was indicated that the oxygen K-edge absorption peak was observed, before the electrode potential reaching the onset potential, i.e., from around 1.0 V vs. relative hydrogen electrode of the electrode potential. It was confirmed that the electrochemical reactions at the solid–liquid interface of metal electrodes like the OER catalyst are able to be observed in real-time.