However the discussion of three-phase boundaries, and by extension, the three-phase length cannot be complete without accounting for various factors that influence the local spatial distribution of ionomer chains around catalyst particles. It is known that the balance between the hydrophobicity of carbon particles and the hydrophilicity of Pt particles influences the local distribution of ionomer chains. This is further complicated by the migration of ionomer chains due to factors like Ostwald ripening of Pt particles and carbon corrosion . However, these local phenomena are beyond the resolution and scope of this work. Herein we intended to discuss and capture the meso-scale aggregation phenomena observed in the CL fabrication process.