Investigating the Catalyst/Ionomer Interface in PEM Water Electrolysis Using Microelectrodes

Abstract

Low temperature zero-gap PEM water electrolyzers are promising devices which are still in development. Water electrolyzers have the potential to be a critical part of the energy transition as a method to use renewable electricity to produce hydrogen which can feed into the hydrogen economy. When paired with renewable sources of electricity, electrolyzers will be subjected to variable power loads, which places a large stress on the systems. This stress causes increased degradation of many components, including the catalyst layers. It can be challenging to study the impact of degradation of the catalyst layer in an electrolysis cell, due to the many coupled degradation phenomenon occurring in the full cell system. Microelectrodes can be used to investigate the catalyst layer under electrolysis operating conditions, but in a simplified system which can more easily isolate the catalyst layer and kinetics. One of the limiting factors in water electrolyzer performance is the oxygen evolution reaction (OER) due to the sluggish kinetics. If the OER kinetics could be improved, it would greatly reduce the cost of the electrolyzer system. The ionomer forms a thin film in the catalyst layer, and controls the local conditions surrounding the catalyst. The local conditions and interactions of the ionomer with the active catalyst sites still aren't well understood, as well as the contribution of the ionomer to catalyst degradation. In this study, cavity microelectrodes will be used to investigate the impact of ionomer on IrOx catalyst OER performance and durability.