Reconsidering the Benchmarking Evaluation of Catalytic Activity in Oxygen Reduction Reaction

The sluggish kinetics of the oxygen reduction reaction (ORR) on electrocatalysts represents a major obstacle in the development of fuel cell technology. A tremendous amount of work has reported the increasing ORR activity for catalysts. Nevertheless, when applied to practical Membrane Electrode Assembly (MEA, an assembled stack of a proton exchange membrane fuel cell) configuration, the high-performance catalysts on the rotating disk electrode (RDE) may not display the same high activity as in the lab-scale tests. This led us to reexamine the ORR evaluation based on the RDE technique. With the development of high active electrocatalysts, it may become significant to determine the reasonable kinetic current at a conventional fixed potential approaching the limited current by using the Koutecky-Levich (K-L) technique on RDE for the evaluation of ORR activity. Here we describe such a challenging situation and systematically discuss the proper kinetic region when comparing the ORR activity with the unsuitable potential or Pt loading based on the K-L technique. Furthermore, the rational benchmarking guidelines are given for the evaluation of the ORR electrocatalysts.