Fig. 1. (a) ORR activity of commercial Pt/C adopted as the reference to evaluate the activity of a catalyst; the real and the measured ORR performance of Pt/C are shown to indicate an unreliable evaluation (Δ vs. Δ') of a catalyst with Pt/C as the reference. The unreliable measurement of ORR performance for commercial Pt/C can promote the underestimation or overestimation of the ORR performance of a catalyst. (b) The measurement of the ORR half-wave potential of a catalyst from a LSV curve.

Fig. 2. Overview of literature data on the relationship between Pt loading and ORR half-wave potentials (E1/2) in different electrolytes: (a) acid, (b) alkaline. The red curves in (a) and (b) represent the average values of E1/2 at different Pt loadings.

Fig. 3. (a) Statistical analysis of the adoption of size-different GC electrodes globally in both acid and alkaline solutions for commercial Pt/C-electrocatalyzed ORR; (b) Average half-wave potential obtained on commercial Pt/C supported by size-different GC electrodes with Pt loading in the narrow range of 20 ± 2 μg/cm2 in both acid and alkaline solutions.

Fig. 4. Statistical analysis of the scan rate dependent half-wave potential in different electrolytes based on the data obtained on a 4-mm electrode with Pt loading in the narrow range of 20 ± 2 μg/cm2.

Fig. 5. Overview of literature data on the relationship between Pt loading and the ORR half-wave potentials (E1/2) in HClO4 (0.1 M) and H2SO4 (0.5 M).

Fig. 6. Statistical analysis of the half-wave potential of Pt/C produced by different companies in both acid (a) and alkaline solutions (b).

Fig. 7. Pt loading and electrode size-dependent ORR performance (E1/2) of commercial Pt/C in 0.1 M HClO4 (a) and 0.1 M KOH (b) electrolytes. The scanning rate was set to 10 mV/s for all measurements.

Fig. 8. LSV curves of commercial Pt/C on a glassy carbon electrode with a 4-mm diameter and Pt loading of 20 μg/cm2 in 0.1 M HClO4 and 0.5 M H2SO4. Inset is the averaged ORR half-wave potential.