Metal Nitride Controlled Atomic Doping of Mo^x+ in NiFe (Oxy)Hydroxide to Trigger Lattice Oxygen‐Mediated Mechanism for Superior Oxygen Evolution

Abstract The covalency of the metal─oxygen (M─O) bond is significantly amplified in the transition metal sites with elevated oxidation states, thereby enabling the lattice oxygen‐mediated mechanism (LOM) to transcend the traditional linear scaling limitations of the oxygen evolution reaction (OER). Here, an innovative surface atom release speed‐mediated doping of Mo atoms in NiFe (oxy)hydroxides by controlled dissolution of Mo atoms from the Mo₂N surface, which resulted in the formation of NiFeMo(OH)₂ with high valence Ni species for OER. Structural characterizations, coupled with in situ Raman and theoretical calculations, elucidate that the incorporation of Mo in NiFeMo(OH)₂ modulates the electronic configuration of the metal centers, thereby diminishing the formation energy of Ni 3+/4+ species. This modulation augments the M─O bond covalency, facilitating a shift in the OER pathway from the conventional absorbate evolution mechanism to the more efficient LOM. Consequently, the NiFeMo(OH)₂ displays a low overpotential of 236 mV at a current density of 10 mA cm⁻², along with long stability (>500 h) at 50 mA cm⁻². Furthermore, when integrated into an anion exchange membrane water electrolyzer, it achieves a current density of 1.0 A cm⁻² at a cell voltage of merely 2.27 V, underscoring its potential for practical applications.