We next attached the optimized (ZnO) 3 to graphene and to each GO model before reoptimizing the composite system. The (ZnO) 3 cluster is bonded via the Zn2 atom ( (ZnO) 3 adsorption energies on graphene and GO models are of interest with respect to their stability as catalytic sites, and were calculated using eq 2 and eq 3 in kcal/mol respectively with the results displayed in the table 2 along with the free energy and enthalpy change of adsorption at 300K.