Lock-and-Key Intermediate Binding on Spinel Octahedra Enables Selective Urea Electrolysis.

Selective urea electro-oxidation to benign N2 gas over toxic ionic byproducts is crucial for sustainable hydrogen production and wastewater remediation, yet achieving the desired N─N coupling remains a formidable challenge. In this study, we propose an atomic-scale geometric matching strategy by pioneering an edge-sharing octahedral bridged spinel catalyst (MNCON). Through Mn3+ incorporation into an N-modulated inverse NiCo2O4 platform, we construct a robust Nioct─O─Mnoct edge-sharing network that precisely matches the interatomic spacing required for bridge-coordinated binding of key intermediateds and promotes electron delocalization. This structural synergy stabilizes the critical *NHCONH intermediate, lowers the thermodynamic energy barrier by 1.74 eV relative to the counterpart, and significantly accelerates N─N coupling. Consequently, MNCON simultaneously steers product selectivity toward benign N2/CO2 with detrimental ionic byproducts reduced by approximately fourfold compared to NCO and delivers a UOR potential of 1.41 V vs. RHE at 300 mA cm-2. The catalyst maintains structural durability for 500 h at 500 mA cm-2, alongside steady hydrogen evolution reaction (HER) performance. Integrated into a UOR||HER electrolyzer, the symmetrical cell operates stably for over 400 h in artificial urine at a low average cell voltage of 1.31 V (10 mA cm-2). This edge-sharing accommodation paradigm provides a viable route for designing highly selective electrocatalysts.