The Influence of Nafion Content on Catalytic Oxygen Reduction Performance of High Surface Carbons

ABSTRACT High efficiency and selectivity of the electrocatalytic oxygen reduction reaction (ORR) requires fast proton, electron, and oxygen supply to the catalytic center. The kinetics of these processes depend largely on the preparation of the catalyst‐containing electrode. Specifically, the type and amount of ionomer binders is crucial for the reaction performance. Nafion is currently the most frequently used ionic binder material enabling surface distribution of catalytic sites and fast proton transfer. Yet, the role of Nafion content for specific catalyst materials is not analyzed in depth, resulting in poor reproducibility and comparability between laboratories. In this work, we focus on the influence of Nafion content in particular regarding high surface area carbon electrodes for the ORR. The chosen carbon‐based materials varied in their surface area and the amount of active oxygen, nitrogen, or iron sites, leading to different catalytic activities. The selection of Nafion content leads to differences in onset potential of up to 70 mV while currents varied about 2 mA/cm 2 . For all electrode materials, an ideal Nafion content regarding reproducibility and performance could be identified. Based on our results we derive an estimation on how to choose the Nafion content based on the specific surface area (SSA) of the electrocatalyst.