Figure 4.

(a) Experimentally determined Tafel plots for different catalysts from ORR polarization curves shown in Figure S3, SI, data were collected at RDE = 1600 rpm. (b) Volcano plot between j₀^theory and ΔG_OOH* with charge-transfer coefficient α = 0.5 (red dashed line). Blue hollow squares are j₀^expt obtained from Tafel plots and DFT-derived ΔG_OOH* for each doped graphene catalyst. ΔG_OOH* for X-graphene (blue solid square) was obtained from eq S4e, SI and its j₀^theory was obtained from eq 10. The j₀^expt value for Pt was also shown by the blue dashed line as a reference.