Non‐Equilibrium Construction of Layered Ruddlesden–Popper La ₂ NiO ₄ Porous Nanosheets for Efficient Urea Electrooxidation

ABSTRACT Urea electrooxidation offers a low‐voltage pathway for hydrogen production while simultaneously addressing nitrogen‐cycle remediation, yet its multi‐step mechanism is kinetically hindered by sluggish C–N bond cleavage and the accumulation of strongly adsorbed intermediates. Conventional nickel‐based oxides suffer from limited exposure of Ni–O active sites and slow charge redistribution, restricting overall catalytic turnover. In this study, a microwave shock strategy was developed to construct two‐dimensional porous La 2 NiO 4 nanosheets with a well‐defined Ruddlesden–Popper ( n = 2) layered structure. The ultrafast non‐equilibrium synthesis generates transient supersaturation and controlled gas evolution, promoting the formation of open interlayer channels and abundant oxygen vacancies. This architecture enhances mixed ionic–electronic transport and facilitates rapid proton‐coupled electron transfer during urea oxidation, yielding a low onset potential, high mass activity, and excellent durability. Mechanistic analysis reveals that the coexistence of Ni 2+ /Ni 3+ redox couples and oxygen defects strengthens Ni 3 d –O 2 p hybridization, narrows the band gap, and accelerates charge redistribution. The results establish a structure–defect–activity correlation for layered nickelates and show that microwave‐induced non‐equilibrium synthesis provides a versatile route for designing metastable oxides. This work advances the understanding of structure‐driven electrocatalysis and offers a strategic framework for future energy–environment catalytic technologies.