Ni-Activated Atomic Fe/Fe–Ni Heterosites for Decoupled C–N Coupling in Urea Electrosynthesis

Abstract

The electrocatalytic co-reduction of nitrate (NO3−) and carbon dioxide (CO2) into urea represents a potential avenue for achieving efficient urea production. However, this process involves intricate C–N coupling reactions and faces a severe kinetic mismatch between the reduction pathways. This disparity typically leads to a disproportionate coverage of key C- and N-containing intermediates on the catalyst surface, resulting in dominant competitive side reactions. Herein, we report the design of a heterogeneous FeNi@AC catalyst that integrates isolated Fe single atoms and Fe–Ni dual-atom sites at the atomic scale, enabling the efficient conversion of NO3− and CO2 into urea. Combined experimental and theoretical investigations reveal that the isolated Fe single-atom sites retain high nitrate reduction capability. Crucially, the introduction of Ni induces an electronic reconfiguration of the Fe center, which significantly lowers the energy barrier for CO2 activation (from 0.7 eV to 0.1 eV). This activation effectively bridges the kinetic gap between C- and N-species. Consequently, the FeNi@AC catalyst achieves a urea yield rate of 13.6 mmol g–1 h–1 and a Faradaic efficiency of 51.7% at –0.8 V (vs RHE). This work not only presents an active catalyst for urea synthesis but also provides a site-specific regulation strategy for designing multifunctional atomic-site catalysts tailored for complex tandem reactions.