Parameter Decoupling and Standardization of an RDE Protocol for CO Tolerance Evaluation of the Alkaline Hydrogen Oxidation Reaction

CO poisoning remains a major challenge for hydrogen fuel cells, and rotating disk electrode (RDE) measurements are widely used for preliminary screening of CO-tolerant catalysts. However, variations in key testing parameters, including catalyst loading, CO exposure time, and linear sweep voltammetry (LSV) scan rate, can substantially affect the apparent CO tolerance response and compromise cross-study comparability. Here, Pt/C was employed as a model catalyst to systematically decouple the effects of these parameters on CO tolerance evaluation of the hydrogen oxidation reaction (HOR). Catalyst loading was identified as a critical factor: at a low Pt loading of 5 μgPt cm−2, CO adsorption caused a severe decrease in the HOR limiting current, whereas at a high loading of 40 μgPt cm−2, excess available Pt sites markedly diluted the apparent poisoning effect. Electrochemical impedance analysis further revealed distinct loading-dependent changes in interfacial charge-transfer and mass-transport processes under CO-containing conditions. In addition, prolonged CO pre-exposure increased surface poisoning and current loss, while slower LSV scanning amplified the apparent poisoning response by extending the effective CO exposure time. Based on these findings, we propose a standardized RDE evaluation principle based on low catalyst loading, sufficient CO pre-exposure, and slow potential scanning, providing a more reproducible and comparable benchmark for evaluating catalyst-dependent resistance to CO poisoning under controlled RDE conditions.