Electron Delocalization in Ni–Co Active Pairs for Efficient and Robust Urea Electrooxidation

Ni(OH)₂ is a promising urea oxidation reaction (UOR) catalyst, yet its performance is fundamentally limited by electron localization in Ni^II that hinders the formation of active Ni^III species. Herein, we overcome this limitation by constructing electron-delocalized Ni-Co active pairs (Ni^II+δ-O-Co^II+δ) through Co doping of Ni(OH)₂ and integration with a CoNi alloy. This architecture exploits work-function-difference-driven charge transfer to delocalize Ni^II 3d electrons, thus accelerating the Ni^II/Ni^III transformation and achieving an ultralow UOR potential of 1.288 V_RHE at 10 mA cm^-2, outperforming Ni^II+δ-O-Ni^II+δ (1.333 V_RHE), Ni^II-O-Co^II (1.349 V_RHE), and Ni^II-O-Ni^II (1.365 V_RHE). Concurrently, the electron-delocalized Ni-Co pairs with upshifted d-band centers enhance N-terminal urea adsorption and Ni/Co-N charge transfer, which weakens N─H bonds and reduces the energy barrier of the rate-determining step (CONH₂NH₂ ^* → CONH₂NH^*). The strengthened metal-O bonding suppresses dissolution, achieving record stability for 2100 h across 10-500 mA cm^-2. Applied in a urea/urine electrolyzer, this catalyst enables energy-saving hydrogen production (3.68/3.74 kW h m^-3 at 100 mA cm^-2), providing a dual-purpose solution for sustainable energy and environmental remediation.