Dynamic ligand-vacancy engineering drives metal dimerization for efficient urea electrooxidation.

The electrochemical urea oxidation reaction offers environmental benefits by enabling hydrogen generation and nitrogen recycling. However, catalyst instability caused by surface reconstruction remains a challenge. Here, we develop a heteronuclear vacancy-to-bond strategy that achieves both catalytic activation and structural preservation via atomic-level self-optimization. Using Fe-doped bimetallic frameworks, we construct a self-adaptive coordination microenvironment that dynamically generates controllable ligand vacancies while promoting metal dimerization, leading to shortened interatomic distances. The resulting ligand-vacancy-mediated stabilization delivers an low potential of 1.222 V @ 10 mA cm-2 (188 mV lower than IrO2) with 87.7% Faradaic efficiency for nitrogen oxides. Spectroscopic analysis and theoretical calculations reveal that ligand-deficient structure reduces the C-N cleavage energy from 1.33 eV to 0.75 eV and shifts the rate-determining step from chemical C-N cleavage to potential-dependent *NO oxygenation, lowering the overall energy requirement. In industrial-scale electrolyzers, the catalyst sustains 1 A cm-2 for 100 h with negligible degradation, achieving 13% energy savings over conventional water splitting. This work investigates a dynamic vacancy-to-bond conversion mechanism, offering insights into the design of adaptive electrocatalysts for sustainable energy applications.