Revealing voltage threshold for reaction site distribution on PEM electrolyzer electrode using direct bubble visualization and modelling

Reaction mechanism, like the reaction site distribution on the catalyst layer, is crucial for PEM water electrolyzer development. Here, we analyze how input voltage affects the reaction site distribution using a visible coplanar electrode proton exchange membrane water electrolyzer (PEMWE). It is discovered that the reaction site distribution is in a limited range at the responding input voltage and there is a positive correlation due to the non-uniform potential distribution. Based on these findings, we define the concept of “voltage threshold” and further optimize a previous numerical model of the catalyst layer by introducing the reaction onset voltage. The strong agreement between experimental and simulation data resulting from the developed model demonstrates its feasibility. These results provide a novel perspective, method, and numerical model for a more comprehensive and realistic assessment of the reaction site distribution inside the electrolyzer.