Xuena Gao, Yihan Zhao, Jiaxin Tu, Chunmei Ni, Jing Li, Ju Wang, Wenyi Tan, Xiaoyan He, Zhao Li, Lin Tian
A NiCo-LDH/CeO2 heterostructure catalyst was constructed for urea oxidation and oxygen evolution. The optimized catalyst exhibits low overpotentials and high stability, with a water-splitting device achieving 500 mA cm-2 at 1.83 V in 1 M KOH. Built-in electric field and oxygen vacancies synergistically enhance the catalyst's activity.
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/CeO2 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 CeO2 and promotes surface reconstruction into highly active NiCoOOH species. CeO2 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.