Durst et. al. refers to QE based microkinetic models by K. Krischer and Savinov to decide on the reaction path for the HOR/HER in PEM fuel cells. Similarly, in the research of the ORR the proposed 2e -and 4e -reaction paths are supposed to be distinguishable through a Tafel slope of 59 mV/decade and 118 mV/decade, respectively, as discussed by Schmidt et. al. and by Adžić et. al. for the ORR on gold, employing again the QE assumption. Fletcher