fig4

Figure 4. Theoretical simulations of K atom adsorption and diffusion in different structures. (A) Top view of K⁺ adsorbed in graphene, along with N, O doping; N doping and O doping structures, and the related adsorption energies. (B) The corresponding side view of the electron density changes of the K atom adsorbed on these structures, and yellow and blue spots represent raised and reduced electron densities, respectively. (C) Top view of the structures with K atom diffusion and associated diffusion energies. The atoms C, N, O, and K are represented by the brown, silver, red, and purple balls, respectively. Copyright 2020, Nano Energy. Theoretical simulations of K adsorption in different structures^[11].