According to these energetically favored adsorption sites, the number of H atoms that can be adsorbed on the Ir cuboctahedron surface (for a given m, denoted NH,Ir) can be calculated as follows (Equation (4)): (4)NH,Ir=N1(5)+N1(9)+N2(5,5)+N2(5,7)+N2edge(7,7)+0.5×N2(7,8)+0.5×N2(8,8) where the 0.5 coefficient is used to obtain a coverage of 1 monolayer with N2(7,8) and N2(8,8) .