True gas phase oxygen reduction reaction (ORR) explorations at the electrolyte/gas interface: A unique screening configuration to study electrode interface structure for PEMFCs

To evaluate the oxygen reduction reaction (ORR) performance of the GDEs, we established a simple and cost-efficient procedure based on a classic three-electrode liquid electrolyte electrochemical cell, where the GDE being studied is kept only partially submerged in the liquid electrolyte, creating a critical electrode/electrolyte/outer atmosphere interface. The work successfully demonstrates that the hanging GDE configuration (HGDE) can be applied to study the ORR performance based on a genuine GDE interface structure in a vicinity of air or oxygen and proton conduction phase, where it allows high ORR currents due to access to the gas phase oxygen. In contrast, the conventional setup uses a completely submerged configuration, where the ORR current is limited by the solubility of oxygen in the electrolyte. Despite the fact that in HGDE configuration, the active area at the electrolyte/gas interface resembles to the completely flooded conditions in a PEMFC configuration, the measured ORR performances of the HGDEs with different electrode structures (catalyst/ionomer ratios) correlate qualitatively with the PEMFC single cell tests. This near negligible phenomenon and proven methodology carry immense potential towards efficient parameter screening on GDE based electrode interface development, which ensures advancement of PEMFC technologies and beyond. • A simple setup for gas diffusion electrode (GDE) characterization is introduced. • The proposed hanging GDE setup can be used to study interface structure in GDEs. • ORR activity measured using hanging GDE correlates well to single cell performance.