As Figures and show, MN4/G have only shown limited improvement in scaling relations between ΔG*OH and ΔG*OOH than pure metal surfaces . The main reason lies in the large intercept value (3.2 eV) in the scaling equation (ΔG*OOH = 0.75ΔG*OH + 3.2) favors a weaker binding of *OOH. An incremental tuning the first coordination shell of MN4 site (MN3C/G, MN2C2/G, and MC4/G) by replacing N atoms with C atoms does not make significant change (Figures and), suggesting that fine-tuning first coordination shell may be ineffective in altering scaling relations in OER. Note that we used adsorption energies instead of adsorption free energies in the test of variants of MN4/G, because the difference between these two energy terms is contributed by zeropoint energy and entropy item of adsorbates, which we expect are comparable before and after the adsorption and will not appreciably affect the scaling relations.