Spin Polarization Enables Spin-Conserved Intermediate Migration for Selective C–N Coupling toward Urea Electrosynthesis

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Electrochemical coreduction of CO2 and nitrate to urea offers a promising approach to carbon–nitrogen fixation but still suffers from sluggish C–N coupling and severe competition from ammonia formation. Existing studies primarily focus on intermediate adsorption and largely overlook the spin-state changes that occur during intermediate transformation and C–N coupling. Herein, we introduce a Cu-modulated spin-regulation strategy where Cu substitution subtly modulates the Fe electronic configuration of FeSe2 to generate spin-polarized Fe centers. We reveal that mixed-valence Fe species in Cu-FeSe2 induce a double-exchange-like spin polarization, which facilitated the migration of N-containing intermediates between neighboring Fe sites, thereby promoting C–N coupling. As a result, the Cu-FeSe2 catalyst achieves a urea Faradaic efficiency of 54.1%, a yield rate of 78.5 mmol h–1 g–1, and an electrochemical stability over 75 h. Supported by operando spectroscopic analyses and density functional theory (DFT) calculations, the spin-polarized Fe centers stabilize *COOH and *NH2 intermediates while suppressing over-hydrogenation to ammonia. This work highlights spin polarization as a promising strategy for constructing efficient electrocatalytic sites and enabling multi-intermediate electrocatalysis toward urea synthesis.