Dual spillover of carbon monoxide and hydrogen initiates tandem urea electrosynthesis

Electrochemical urea synthesis from CO₂ and NO₃^- provides a sustainable alternative to industrial processes, yet remains challenged by inefficient C-N coupling and protonation. Here, we present a tandem urea electrosynthesis pathway over copper-supported palladium hydride (PdH_x/Cu) through a dual spillover of CO* and H*. This pathway undergoes efficient CO₂-to-CO* conversion on PdH_x and facile NO₃^--to-NO* conversion on Cu. Crucially, rapid spillover of CO* (from PdHx surface) and H* (from PdH_x lattice) to Cu facilitates key C-N intermediate (OCNO*) formation and protonation, respectively. Our catalysts demonstrated high performance, achieving a urea production rate of 236.5 ± 8.9 mmol g_cat^-1 h^-1 with a Faradaic efficiency for urea of 62.6 ± 1.8%. With these catalysts, our scaled-up flow cell enabled continuous co-production of urea and formate with consistent profitability and much lower CO₂ emissions compared to these for the present-day urea production route. This achievement represents a significant step for sustainable urea production.