Impurity-Driven Interfacial Reconstruction Unlocks Highly Active Sites in Ni–Fe Selenides for Water Oxidation
Yeongeun Jang, Min‐Kyu Son, Seunghwa Lee
Abstract
Understanding how surface-active sites emerge during electrochemical operation is critical for advancing oxygen evolution reaction (OER) catalysts. In this study, we investigate the dynamic reconstruction behavior of nickel (Ni)–iron (Fe) selenide systems, with a particular focus on the role of selenium (Se) in facilitating surface reorganization and activating Fe species. Through a comparative analysis of bulk-doped NiFeSe, surface-adsorbed Fe–NiSe, and sequentially modified Se1–Fe2–Ni systems, we demonstrate that catalytic performance is strongly governed by interfacial dynamics rather than bulk composition. Operando Raman spectroscopy and XPS analyses reveal that the formation of Se–Se species and Fe 3+ in selenide environments are key signatures of active site generation. While NiFeSe follows a relatively static transformation pathway, Fe–NiSe and Se1–Fe2–Ni exhibit distinct interfacial restructuring driven by Se dissolution and impurity-stabilized readsorption. These processes lead to the formation of highly disordered but intrinsically active surface phases, resulting in enhanced OER kinetics.