The most favourable NHx-terminations are 1ML NH and 1ML NH2, which yield 4NH+4NH2 on the (2×2) supercell (Figure , SI) and 9NH+9NH2 on the (3×3) supercell (Figure ). NH occupies the surface bridge sites and NH2 occupies the surface top sites, which is similar to our previous reports of favourable NHxterminated Ru and Co surfaces . H atoms from surface top NH2 and surface bridge NH are referred as surface H and bridge H when we describe the ligand exchange reactions.