The rotating disc electrode: measurement protocols and reproducibility in the evaluation of catalysts for the oxygen evolution reaction

A measurement protocol for the evaluation of catalyst inks for the oxygen evolution reaction via rotating disc electrode measurements was conceived and applied in a multi-partner project. It was found that the electrochemical performances determined for a standardized electrode based on nickel-cobalt-oxide in 1 M KOH show a spread in the range of 50 mV at 10 mA cm-2, when comparing results from different groups. The variation of results obtained within individual groups, on the other hand, were found to be significantly lower. From this finding, we argue that the characterization of catalyst inks via rotating disk electrode measurements is strongly affected by individual sample preparation and handling, leading to an additional uncertainty that depends on the individual experimenter. Consequently, the use of this technique for the evaluation and comparison of catalysts for the oxygen evolution reaction needs to be discussed and potentially revisited. Elaborated and uniform experimental protocols are a prerequisite for OER catalyst evaluation via RDE. Still, individual sample preparation and variations in microenvironment can lead to a significant spread of results between different laboratories.