Visualization of Oxygen Bubbles on a Flat Ionomer-Coated Platinum Electrode

To improve the performance of polymer electrolyte membrane water electrolyzers (PEMWE), it is necessary to grasp oxygen transport from the reaction site. This paper presents a visualization study which examines the effect of ionomers on the behavior of oxygen bubbles generated from catalyst covered with ionomers. The bubbles are captured with a high-speed camera, and the post visualization by electron microscopy with EDX showed that there were no significant cracks and damages on the ionomers. This implies that oxygen bubbles are generated on the ionomer surface without an apparent three-phase boundary (i.e., catalyst-ionomer-water). This suggests oxygen generated on the Pt surface was transported as dissolved oxygen through the ionomer layer.