In Situ XANES and DFT Insights Into Hierarchical NiCoFe Catalysts for Highly Active and Durable Oxygen Evolution and Urea Oxidation

ABSTRACT

NiCoFe layered double hydroxide (NiCoFe‐LDH) and surface‐reconstructed NiCoFe alloy (ANiCoFe) electrocatalysts were systematically investigated for alkaline oxygen evolution (OER) and urea oxidation (UOR). In situ X‐ray absorption near‐edge structure (XANES) analysis, density functional theory (DFT), and XANES simulations were employed to investigate the potential‐dependent redox behavior, phase reversibility, and local coordination environment of the catalysts. While both catalysts exhibit comparable activity at low current density, ANiCoFe demonstrates superior performance at higher current densities, delivering lower overpotential and higher turnover frequency (TOF). After prolonged cycling, ANiCoFe requires a lower potential to achieve 40 mA cm ^{− 2} compared to NiCoFe‐LDH, indicating enhanced durability under practical conditions. In situ XAFS reveals reversible Ni ^{2 +} /Ni ^{3 +} redox transitions during operation, while DFT‐assisted XANES analysis identifies the local coordination environment of Fe species within the ternary framework. Notably, the reconstructed ANiCoFe structure, featuring a conductive metallic core, suppresses the formation of isolated γ‐NiOOH domains and enhances phase reversibility under dynamic potentials. Consequently, ANiCoFe exhibits excellent catalytic activity, high intrinsic activity (TOF), and long‐term stability for both OER and UOR, including under intermittent on–off electrolysis, highlighting its promise as a cost‐effective non‐noble‐metal electrocatalyst.