fig5

Figure 5. Seven calculation models after K⁺ absorption on (A) G-C, (B) N5-C, (C) N5/P-C, (D) N6-C, (E) N6/P-C, (F) NQ-C (graphite-nitrogen doped carbon) and (G) NQ/P-C. (H-N) Charge density difference of various models. (The isosurfaces level = 0.0015 e Bohr-3. The cyan areas represent charge depletion; the yellow areas represent charge accumulation, and the brown, red, blue, and green balls represent C, N, P, and K atoms, respectively).