HFR [mΩ cm However, while kinetic performance that is comparable to the d-Pt-Ni/C-JM benchmark is already a good indication, it by far does not reveal the entire story. For that, we need to look at the 50 cm 2 single-cell ORR polarization curves and thus, HCD performances at various conditions (Figure ). Namely, both A and S-activated catalysts were compared in both O2 and air, as well as at both 'hot-wet' (80 o C, 100% RH on both the cathode and the anode) and 'hotdry' (80 o C, 30% RH on both the cathode and the anode) conditions. Figure shows the comparison of 50 cm 2 single-cell ORR polarization curves between d-Pt-Ni/C-NIC-A and d-Pt-Ni/C-NIC-S electrocatalysts in 'hot-wet' conditions in both O2 and air. Interestingly, no significant difference is observed in O2 performance for both A and S-activated catalysts up until 2 A cm -2 geo, whereas impressively, the voltage has not yet dropped below 0.7 V. In contrast, in accordance to expectations, performance of both A and S-activated catalysts drops significantly when O2 on the cathode is exchanged for air. Nevertheless, both catalysts still achieve an impressive 1.4 A cm -2 geo at 0.6 V with the cathode loading of S-activated catalyst being only ~82 µgPt cm -2 (Table ). Here we wish to emphasize to the reader that no effort was put into catalyst ink/layer optimization in the case of Pt-M NIC electrocatalysts as part of this study, but rather, these parameters were translated based on the previous work by JM .