We utilized a 20 Å vacuum gap to remove periodic interaction in perpendicular direction. The kpoints mesh were chosen to 5 × 5 × 1 at the Brillouin zone using the Monkhorst-Pack scheme. The geometry optimization criteria were set to 10 -6 eV for energy convergence and 0.01 eV Å -1 for forces on each atom respectively. The high spin state was achieved by setting initial magnetic moments on the Ni atom, followed by the geometry optimization. For binding energy calculations, we used H2, O2, and NO and CO molecules and graphene system for reference energies.