Built‐In Electric Field and Oxygen Vacancies Synergistically Enhance NiCo‐LDH/CeO ₂ Bifunctional Catalyst

The development of bifunctional electrocatalysts for urea oxidation and oxygen evolution is crucial for stable anodic reactions and efficient cathodic hydrogen production. Herein, a NiCo‐ (including the 1 μm‐scale SEM image in (f))LDH/CeO ₂ heterostructure catalyst is constructed on nickel foam via two‐step electrodeposition. The optimized catalyst exhibits remarkable bifunctional activity. At 100 mA cm ⁻² , the overpotentials are 329 mV for oxygen evolution and 139 mV for urea oxidation. The assembled water‐splitting device achieves 500 mA cm ⁻² at 1.83 V in 1 M KOH. This voltage decreases by 100 mV upon adding 0.33 M urea, with 200 h stability. Mechanistic studies reveal that energy band mismatch induces a built‐in electric field. This drives electron transfer from NiCo‐LDH to CeO ₂ and promotes surface reconstruction into highly active NiCoOOH species. CeO ₂ introduction also significantly increases oxygen vacancy content, facilitating water activation and enhancing reaction kinetics. This work provides a promising strategy for high‐performance LDH‐based bifunctional electrocatalysts.