For the reactions involving the metal precursors RuCp2 and CoCp2, the van der Waals correction was applied with the PBE-D3 method to ensure an accurate description of adsorption energy and reaction energy. When single metal precursors are placed on the surface, the coverage of metal precursors is 0.75precursor/nm 2 for our (3×3) surface supercell model. Charge transfers were analysed with Bader charge analysis procedure. This was computed by q(Bader) -q(valence).