Because single-cell testing is time consuming, requires relatively large amounts of the electrocatalyst (in contrast to TF-RDE) and is highly complex in nature (many parameters can influence performance), it is highly important to be able to have a preliminary and facile method of distinguishing between a 'poorly' or 'adequately' de-alloyed (activated) Pt-alloy electrocatalyst. Providing such a solution has been one of the core goals of this study. Namely, the data so far suggests that both A-activated analogues not only exhibited a larger shift in the potential of the CO-electrooxidation peak maximum (Figures ), but also experienced a higher amount of less noble metal dissolution (Figures ). Thus, based on the evidence presented in this study (as well as our previous reports ) we argue that the potential difference in the CO-electroxidation peak maximum can serve as a very simple and sensitive preliminary indicator that can help distinguish between a 'poorly' or 'adequately' de-alloyed (activated) Pt-alloy electrocatalyst. The effect of the less noble metal ions on the position of the CO-electrooxidation peak has already been explored on the Pt/C electrocatalyst by Durst and co-workers . In their study, they have spiked the electrolyte with different amounts of various metal ions and observed shifts in the position of the CO-electrooxidation peak towards more negative potentials. This occurs because less noble metal ions induce a more facile (hydr)oxide formation at the Pt surface in the double layer. Hydrated less noble metal cations are located between the inner and outer Helmholtz plane where they partially lose their hydration shell and come closer to the Pt surface, inducing increase in the OHad coverage that can cause the shift in the onset of CO-electrooxidation towards lower potentials . Following this study, we have explored this on Pt-alloys as part of our previous work where also a more 'mild' electrochemical activation (potential hold activation) resulted in a shift of COelectrooxidation peak maximum towards lower potentials in comparison to a harsher one (potential cycling activation) . However, the present study for the first time provides the necessary data that correlates this effect with 'real' electrocatalyst samples based on the used chemical activation protocol (A or S-activation). Thus, if our assumption are correct, a similar correlation should be observed when performances of A-and S-activated Pt-M NIC analogues are evaluated in the 50 cm 2 single-cells.