fig6

Figure 6. (A) Top and front views of the different models for P-doped FeN₄-CNS. (B) Calculated free-energy diagram of ORR and OER at the equilibrium potential (1.23 V). (C) Free energy of ORR and OER limiting steps for the models. Gray, red, blue, purple, white and pink spheres represent C, O, N, Fe, H and P atoms, respectively. Reproduced with permission: Copyright 2016, American Chemical Society^[122]. (D) Schematic model of Fe-SAs/NPS-HC with Fe (orange), N (blue), P (green), S (yellow) and C (gray) atoms. (E) Calculated charge density differences of Fe-SAs/ NPS-C with yellow and blue areas representing charge density increase and reduction, respectively. (F) Free-energy diagram of ORR on different catalysts. (G) The linear relationship between OH* binding energy and Bader charge of different catalysts. Reproduced with permission: Copyright 2018, Springer Nature^[123]. (H) Optimized Mn-N₃O₁ structure with ORR intermediate states OH*. The configurations are illustrated both from top and side views. Black, blue, cyan, red and white balls represent C, N, Mn, O and H atoms, respectively. (I) Free-energy diagram of ORR on Mn-N₁O₃, Mn-N₂O₂ and Mn-N₃O₁ surfaces under 0.4 V. (J) Local density of states of Mn d-orbitals in Mn-N₁O₃, Mn-N₂O₂ and Mn-N₃O₁ structures. Reproduced with permission: Copyright 2018,Wiley^[124].