Atomic Scale Origin of the OER Activity–Stability Trade-Off in NiFe Layered Double Hydroxides: Lattice-Site Oxygen Triggers Fe Leaching

Abstract

NiFe layered double hydroxide (NiFe-LDH) is a representative non-precious-metal catalyst for the alkaline oxygen evolution reaction (OER), yet its long-term stability is compromised by Fe leaching under OER conditions. Herein, using density functional theory calculations and constant-potential ab initio molecular dynamics simulations, we provide an atomic-scale understanding linking high OER activity to the origin of Fe leaching. We reveal that the OER on the reconstructed active NiFeOOH phase preferentially follows an adsorbate-site/lattice-site oxygen coupling (ALOC) mechanism, achieving a theoretical overpotential as low as 0.29 V. Notably, the coupled structure that enables this high OER activity also drives the accumulation of oxygen vacancies. We identify the reconstructed double-oxygen-vacancy structure, formed through solvation-assisted interfacial reconstruction, as the precursor for Fe leaching. Subsequently, an OH^–-assisted coordination/substitution pathway at undercoordinated Fe sites progressively disturbs the octahedral coordination structure, leading to Fe leaching as a tetrahedral FeO₄H species with a rate-determining barrier of 1.05 eV. These findings elucidate how lattice-site-oxygen-involved OER catalysis inherently triggers Fe-leaching-induced deactivation and provide theoretical guidance for stabilizing NiFe-LDH through oxygen-vacancy suppression, lattice-site oxygen regeneration, and local coordination environment strengthening.