Fig. 6.
Binding energy of H* on Ni@CNx models in the presence of Ni adatoms. The dashed line on the bar chart indicates the binding energy of H* on pristine Ni(111) (−2.90 eV). The dash-dotted line corresponds to the optimal binding of H* for the HOR. A cross-sectional view of the most energetically stable geometry for H* on each Ni@CNx model is shown below the chart. Ni, C, N, and H atoms are represented by silver, brown, blue, and green spheres, respectively. Graphene atoms in direct contact with Ni atoms in Ni@CNx models are colored in light brown, while graphene in the second layer is colored in dark brown.