Quantitative decorating Ni-sites for water-oxidation with the synergy of electronegative sites and high-density spin state

Oxygen evolution reaction (OER) is the rate-limiting step in water-splitting. The spin-state transition of H2O/OH- to O2 is the critical contributor to slow kinetics, but has not yet received insufficient attention, and model catalysts with explicit active sites are scarce. Herein, we regulated the electronic structure and spin state density of Ni-sites by introducing transition metals into Ni-MOF (NiM-MOF, M = Cr, Mn, Fe, Co, and Cu). Theoretical calculations and experimental results indicated that OER activity has a volcanic relationship with the d‐band center, where NiFe-MOF was at the volcano summit, showing an ultra-low overpotential of 172 mV at 10 mA cm−2, which was currently one of the highest catalytic activities. Benefiting from the synergistic effect of electronegativity sites and high-density spin state, balanced the adsorption/desorption of intermediates, and minimized the energy barrier for OER. This work provides a new reference for understanding the catalytic mechanism and designing spin electrocatalysts.