Following the Electrochemical Oxidation of Au(111) in Real-Time Using Surface Optical Reflectance and Total-Reflection X-Ray Absorption Spectroscopy

Under electrochemical polarization, many electrocatalysts can undergo oxidation that alters their reactivity and can lead to restructuring and dissolution. In this context, the structure-property relationships of electrocatalysts, as well as their kinetics and dynamic behaviour, are still poorly understood. This knowledge gap mainly relies on the limitations of many traditional spectroscopic and structure determination methods, which cannot be easily coupled in situ with electrochemical methods. In this work, we performed cyclic voltammetry (CV) combined with 2D surface optical reflectance (2D-SOR) and total reflection X-ray absorption spectroscopy (RefleXAFS) in a single operando experiment, to directly follow the electro-oxidation and reduction of a Au(111) model electrode. Our results show that the surface in 0.05 M H 2 SO 4 forms a self-limiting Au 3+ oxide or hydroxide film around 1.5 V RHE during the anodic scan in the CV (2 mV s −1 ), with a thickness of ∼5 Å estimated from the 2D-SOR measurements. The film is then rapidly reduced during the cathodic scan around 1.1 V RHE .