Pulsed Oxidative-Reductive Electrolysis Over Dual Cu and Co Single-Atom Sites for Urea Electrosynthesis

Electrochemical C─N coupling of CO₂ with nitrogen species offers a sustainable route to urea and related chemicals but is constrained under steady-state electrolysis by mismatched reaction kinetics. Here, pulsed oxidative-reductive electrolysis temporally coordinates CO₂ reduction and NH₃ oxidation, regulating the generation and coexistence of carbon- and nitrogen-derived intermediates. Co/CuNC, containing atomically dispersed Co and Cu sites within a nitrogen-doped carbon (NC), achieves a total C─N faradaic efficiency of 42 ± 4%, dominated by urea (20 ± 2%) and ethyl urea (16 ± 2%), with respective yield rates (YR) of 295 ± 25 and 50 ± 5 mmol h^-1 g_cat ^-1. In situ synchrotron x-ray absorption spectroscopy (XAS) reveals potential-dependent changes in Cu and Co oxidation states and coordination environments, while in situ infrared spectroscopy identifies pulse-regulated *CO and *NH_x intermediates and suggests concurrent electrochemical and Wöhler-type pathways. Density functional theory calculations reveal complementary site functions: Cu favors *NH₂ formation, whereas Co more strongly stabilizes *NH_x and *CO intermediates, with *CO also accessible at Cu sites. These findings establish temporal coordination of reactant activation, intermediate populations, and active-site states as a mode-enabled strategy for accessing higher-order C─N products.