Fig. 4

Density functional theory calculation for the OER mechanism. a Free energy diagram for OER on Ru1-N4 (red line), O-Ru1-N4 (blue line), and HO-Ru1-N4 (green line). b Schematic of the whole OER mechanism on Ru-N-C catalyst in the acidic electrolyte. The balls in gray, blue, red, white, and light green represent C, N, O, H, and Ru atoms, respectively. All potentials are normalized to RHE