Oxygen reduction reaction measurements on platinum electrocatalysts in gas diffusion electrode half-cells: Influence of electrode preparation, measurement protocols and common pitfalls

Recently, half-cell gas diffusion electrode (GDE) setups have been presented as a powerful tool and promising alternative to rotating-disk electrode (RDE) as also membrane electrode assembly (MEA) testing of oxygen reduction reaction (ORR) catalysts. While RDE testing aims to extract isolated kinetic data, GDE testing allows characterization of realistic fuel cell catalyst layers at application relevant current densities and potentials, where also phenomena besides catalyst kinetics play a role. Nevertheless, while for RDE as also MEA testing dedicated protocols for reliable electrode preparation and assessment of activity were developed, and are backdrop for trustworthy and comparable data, these are missing for the novel half-cell GDE testing. This work identified key challenges in running and evaluation of half-cell GDE measurements, which are e.g. ink composition and electrode preparation, falsification of electrochemical active surface area using hydrogen uptake measurements, influence of joule heating at high current densities and importance of solution resistance correction. A commercial half-cell GDE, as well as a commercial catalyst, were employed, allowing fast application of the developed protocols, while the general findings can also be translated to other GDE setups.