The Untold Tale of the ORR Polarization Curve

A rotating disk electrode (RDE) is employed to screen materials for the electrochemical oxygen reduction reaction (ORR), which is a key reaction in fuel cells and metal–air batteries. Nevertheless, even more than seven decades after the first report on RDE and the exponential growth of publications on ORR, the following questions remain unanswered: how are the ORR polarization curves related to the fuel cell polarization and power density curves, and what is hidden in the sigmoidal nature of ORR polarization curves? Here, we have made an effort to unveil various aspect of ORR polarization curves and ORR parameters such as the onset, half-wave potential, and diffusion-limited current density from the fuel cell prospective. Interestingly, we find one-to-one mapping among the matrices used to apprise the ORR and fuel cells. It is remarkable that the slope is close to unity for the fuel cell matrices and that it is projected from the ORR polarization curves. This analysis will be a great help to researchers for appraising the suitability of their designed/developed electrocatalysts targeted for fuel cells and metal–air battery applications.