Spatially Matched C-N Coupling within Carbon Defect Confined Interlayer Fe Clusters for Efficient Urea Electrosynthesis.

Abstract

Tailoring spatially matched multi-site structure to simultaneously coordinate CO₂ and NO₃ ^- activation and coupling remains a significant challenge for urea electrosynthesis. Herein, interlayer Fe atomic clusters is constructed (Fe_acs) in expanded 2H-graphitic carbon via a carbon defect-confinement strategy, where spatially matched Fe_acs between graphite layers act as ideal nanoreactors for cooperative C─N coupling. These interlayer Fe_acs are achieved by kinetically modulating cascade reactions (FeO_x reduction, H₂/CO₂-mediated carbon etching, and vacancy trapping) during pyrolysis under H₂/Ar atmosphere with low flow rates. As a result, the interlayer Fe_acs catalyst exhibits a high urea Faradaic efficiency of 39.80% and a normalized production rate of 3643.65 mm h^-1 gFe^-1, which is 7.98- and 9.88-fold higher than control samples (Fe particles without interlayer structure). In-situ fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations further reveal that the spatial matched interlayer Fe_acs structure promotes the adsorption of *CO intermediate and lowers energy barriers for the dehydration of NH₂OH, while carbon defects favor water dissociation kinetics, accelerating subsequent hydrogenation steps and promoting C─N coupling within the interlayer Fe_acs. This work provides a paradigm for designing catalysts with spatial matched active sites for sustainable urea synthesis.