We conducted durability test by operating the cell (Pt0.25Ru0.75/pN-C | Pt/C) at a constant current density of 600 mA/cm 2 at 80 ℃ with both Pt/C and Fe-N-C cathode (Supplementary Figure ). The cell using Pt/C cathode worked steadily with only minimal performance loss in 100 hours, which was attributed to a slight dry-out on the cathode of the cell during operation (the area specific resistance (ASR) increased from 34.7 to 38.6 mOhm/cm 2 ). In comparison, the cell using Fe-N-C cathode have slightly more voltage drop within 50 h, suggesting the source of the deactivation mainly comes from the cathode catalyst. Overall, these results indicate a high stability of Pt0.25Ru0.75/pN-C under the operating conditions of HEMFCs.