Precursor-regulated reconstruction of Cu-based catalysts for efficient electrocatalytic urea synthesis from CO2 and nitrate

Abstract

Electrocatalytic urea synthesis from CO₂ and nitrate provides a sustainable route for coupling carbon utilization with nitrogen-waste upgrading under mild conditions. However, achieving scalable urea yields remains challenging due to the difficulty of synchronizing carbon- and nitrogen-containing intermediates on catalyst surfaces, particularly under practical conditions. Although Cu-based catalysts have been widely studied for C–N coupling, how precursor chemistry regulates their working-state reconstruction during electrolysis is still not well understood. Here, we systematically prepared two Cu-based catalysts enriched with basic surface groups (CO₃²⁻/OH⁻), Cu₂(OH)₂CO₃ and Cu(OH)₂, and investigated their nanoscale reconstruction pathways during electrocatalytic C–N coupling for urea synthesis. Hierarchically structured Cu₂(OH)₂CO₃ delivered a urea yield of 63.20 mmol h⁻¹ g_cat.⁻¹ with a faradaic efficiency of 16.21% at −0.9 V versus RHE, nearly twice that of Cu(OH)₂. Quasi-in situ X-ray photoelectron spectroscopy and X-ray absorption spectroscopy revealed that Cu₂(OH)₂CO₃ follows a carbonate-regulated reconstruction distinct from that of Cu(OH)₂ and maintains a broader mixed-valence working-state window composed of Cu²⁺, Cu⁺, and Cu⁰ during catalysis. In situ FTIR spectroscopy and density functional theory calculations further support a pathway in which CO₂ is reduced to *CO on Cu⁺ sites, nitrate is reduced to *NH₂ on Cu⁰ sites, and their interfacial coupling leads to urea formation. Furthermore, we validated the feasibility of Cu₂(OH)₂CO₃ for electrocatalytic C–N coupling in an environmental scenario of food waste biological treatment. This work elucidates precursor-regulated reconstruction as an effective design principle for promoting selective C–N coupling and advancing more sustainable urea electrosynthesis in complex waste-derived environments.