fig4
Figure 4. Top and side views of N2 adsorbed at the Fe2 site of Fe3@N4C16 with the side-on configuration (A); the end-on configuration (B) with the unit cells marked by black lines; ΔG for the *NN → *NNH step of the energy preferred path for the Fe3@NxC20-x(x = 0~4) materials and the black dashed line indicates the free energy change value for Fe3@C20 (C) and the eNRR free energy diagram over the Fe2 site of Fe3@N4C16 (D). eNRR: Electrochemical nitrogen reduction reaction.
