To further validate whether SCE can effectively enhance OER catalytic performance occurring on M1N4-M2N4/G, we calculated the free energy diagrams covering the full set of elementary steps on six of the selected model systems (Figure 4c). Compared each MN4/G, the counterpart M1N4-M2N4/G enjoys varying degrees of decrease of overpotential with the aid of *OH(M1). Among these M1N4-M2N4/G systems, *OH(Sc) gives NiN4/G the largest improvement (a decrease by 0.57 V) in overpotential, and *OH(Zn) gives IrN4/G the lowest overpotential of 0.24 V. For the reverse reaction of OER, i.e. ORR, the SCE of *OH(M1) will also enhance the ORR activity, as illustrated in Figure . The best combination is ScN4-RhN4/G with an overpotential of 0.22 V in ORR, in which the secondary ligand OH binds to Sc. In summary, our work introduced the concept of secondary coordination environments prevailing in molecular catalysts into heterogeneous SACs and showed the impact of secondary coordination effects on the scaling relationships between intermediates (*OH, *O and *OOH) of OER and ORR. The axial OH bound to the oxygen-philic metal of heteronuclear duo MN4/G catalysts acts as a secondary ligand of active center, alters the scaling relations that shape the theoretical limit of OER and ORR activities on these model systems, and finally leads to improved activities for both OER and ORR. The kinetic simulation results supported the effectiveness of this strategy. Furthermore, the reduction of overpotentials of OER and ORR shown by free energy diagrams is ascribed to the effect of this adjacent axial OH ligand. The computational results disclosing the role of SCE in model SACs offer new insight into the modulation of M-N-C type OER and ORR catalysts, which will provide sparks of the rational design of SACs with enhanced activities in oxygen electrocatalysis for sustainable energy development. In addition, both previous and current work suggest that proper engineering of the secondary coordination sites allows the heterogeneity of binding modes for different intermediates, which is critical for modifying the linear scaling relationship of their adsorption strengths. Therefore, we expect that the modulation of secondary coordination sites may provide an alternative strategy to overcome the hurdle of scaling relationships in heterogeneous catalysis.