Figure 5.

DFT calculations. a) Energy profiles of ORR at U = 1.23 V. b) The relationship between d_d and ΔG _OH*. c) Schematic diagram of the hybridization of d_z2−p_z, d_xz−p_x, and d_yz−p_y. Calculated PCOHP of OH* adsorbed on axial Fe₂N_nc/Fe₁‐N‐C (d), non‐axial Fe₂N_nc/Fe₁‐N‐C (e) and bare Fe₁‐N‐C (f) (The dashed lines indicate the Fermi level). Side view of differential charge density for OH* adsorbed on Fe₂N_nc/Fe₁‐N‐C (g), non‐axial Fe₂N_nc/Fe₁‐N‐C (h), and bare Fe₁‐N‐C (i) (The orange, grey, blue, red, and white balls indicate Fe, N, O, and H, respectively. The yellow and blue colors represent charge accumulation and depletion).