Large-scale hydrogen production using proton exchange membrane water electrolysis (PEM-EL) requires a drastic reduction in the current noble metal content of the electrodes. To achieve this, new analytical techniques for characterizing solid-liquid catalytic interfaces, applicable in operando under a variety of realistic operating conditions, are critical because they provide a deeper understanding of the relationships between catalyst state, structure, and catalytic performance. However, many analytical techniques cannot be applied in liquid environments at realistic potentials and current densities.
We propose electrochemical spectroscopic ellipsometric analysis (ECSE), performed in realistic electrolysis cells, as a new analytical operando method for characterizing electrochemical reactions at solid-liquid interfaces under widely varying working conditions. The method is first validated on a platinum surface using ex-situ and operando ellipsometric analyses. Subsequently, the physico-chemistry of a mesoporous IrOx catalyst film under oxygen evolution reaction (OER) potentials was investigated, showing precise reversible and irreversible potential-dependent variations of a number of physical material properties relevant to catalysis.