fig5

Figure 5. (A) The optimized structures of different active sites on the Ni-Nx surface; (B) The Gibbs free energy profile of CO2RR to CO on gra, gra-N, Ni-N2, Ni-N3, and Ni-N4. The COHP for COOH adsorbed on active site of (C) gra and gra-N, (D) Ni-N2, Ni-N3, and Ni-N4. CO2RR: Carbon dioxide reduction reaction; COHP: crystal orbital Hamilton populations.