Looking now at both A and S-activated Pt-Cu catalysts, the differences become even more significant. Already upon comparison of the performances in 'hot-wet' conditions (Figure ), d-Pt-Cu/C-NIC-S significantly outperforms d-Pt-Cu/C-NIC-A. Interestingly, while the performance of approximately 2 A cm -2 geo at 0.7 V in O2 for the d-Pt-Cu/C-NIC-S is comparable to that of d-Pt-Ni/C-NIC-S, d-Pt-Cu/C-NIC-S achieves an impressive 1.6 A cm -2 geo at 0.6 V in air with a cathode loading of only 88 µgPt cm -2 . When we move into the 'hotdry' conditions (Figure ), similarly to both Pt-Ni catalysts, the performance of d-Pt-Cu/C-NIC-A is once again much worse than that of d-Pt-Cu/C-NIC-S. However, while the HCD performance (air curves) of d-Pt-Cu/C-NIC-S exceeded that of d-Pt-Ni/C-NIC-S under the 'hot-wet' conditions (Figures and), the situation becomes reversed under the 'hot-dry' conditions (Figures and).