Fig. 3: Electrochemical performance measured under gas diffusion electrode half-cell.
a ORR polarization curves measured in gas diffusion electrode half-cell. Measurements were done in 1 M HClO4 electrolyte at room temperature with 200 mL/min oxygen flow and 10 mV/s cathodic scanning rate. Pt wire was used as the counter electrode in the same electrolyte chamber without membrane separation, RHE was used as the reference electrode in a different electrolyte chamber connected with Luggin capillary. Potential was corrected for iR compensation with resistances of 0.87 – 1.08 Ω for all tested electrodes, as obtained from electrochemical impedance spectroscopy. Two electrodes were prepared and measured with ~10 μgPt/cm2 loading to generate the polarization curves. Error bar corresponds to standard deviation from two independent measurements. b ECSA determination via CO stripping for all three catalysts. CO stripping voltammogram (black line) and subsequent CV (red line) of the three Pt/C working electrode (~10 μgPt/cm2) recorded after the ORR measurements at a scan rate of 50 mV/s from 0.1 – 1.1 V RHE at room temperature. Potential was not iR corrected. CO was adsorbed for 5 min at 0.1 V RHE at a flow of pure CO (100 nccm) prior to the CV, followed by a 30 min purging procedure with N2 while maintaining the potential at 0.1 V RHE. To obtain the ECSA, the CO stripping current was integrated using a linear baseline and converted to a corresponding Pt surface area using a specific capacity of 420 μC/cmPt2. c ORR polarization curves normalised by ECSA measured with CO stripping. Error bar corresponds to standard deviation from two independent measurements. d ECSA specific current at 0.8 V for the three catalysts.
