Porous Catalyst Layers for PEMWEs via Electro-Spraying—Achieving Optimal Three-Phase Boundary and Superior Electrolysis Performance

The efficiency of polymer electrolyte membrane water electrolysis (PEMWE) is crucial for realizing green hydrogen production. Since the multiphase complex electrochemical reaction takes place at the three-phase boundary (TPB) in the electrode, the electrochemical kinetics are highly related to the structure and morphology of the electrode. In particular, oxygen and hydrogen bubbles generated during water electrolysis significantly hinder the efficient contact between the electrode and water, lowering the active surface area. In this study, we fabricated porous electrode layers via electrospray and investigated the effect of the ionomer content on the efficiency and durability of PEMWE. Furthermore, the formation of the TPB as a function of the content of ionomer was observed through SEM and measurement of electrochemical accessible surface area. In the single-cell test, our electrode using commercial electrocatalysts exhibited outstanding electrolysis performances of 5.3 A/cm² at 2.0 V and 3.2 A/cm² at 1.8 V. These values are the highest reported compared to recent studies ^[1-8]. In addition to porosity, the ionomer content affected the hydrophobicity and contact resistance between electrode and membrane. Using a simple porosity control technique, the performance of PEMWEs can be improved by over 60%. Therefore, our systematic study on the role of optimal three-phase boundary formation in electrodes is expected to open a new era for the green hydrogen economy.