Atomic-Level Insights into the Cation-Mediated Electrocatalytic C–N Coupling Mechanism over Cu Model Catalyst

Electrocatalytic C–N coupling of organic carbon and nitrogen sources has emerged as a promising route to high-value chemicals in heterogeneous catalysis over the past decade. Most research has focused on optimizing catalyst active sites to accelerate C–N coupling at the catalyst/electrolyte interface, but the electrolyte’s role remains poorly understood. Here, we introduce Li +, Na +, and K + into the electrolyte and use slow-growth molecular dynamics with explicit solvation models to examine their impact on C–N coupling at the Cu/electrolyte interface. We show that K + enables a one-step mechanism in which C–N bond formation and hydrogenation occur simultaneously, yielding the *OC-NOH intermediate with a barrier of 0.68 eV. Differential electrochemical mass spectrometry (DEMS) demonstrates that the m / z = 59, assigned to the *OC-NOH intermediate, is detected over the Cu catalyst in 0.1 M KHCO 3 . Without K +, the reaction follows a two-step pathway with a higher overall barrier of 1.0 eV (0.71 eV for C–N formation, 0.29 eV for hydrogenation), and the *OC-NOH intermediate is not detected by DEMS. Interfacial analysis reveals that K + enriches hydrogen near the interface and enhances charge transfer to activate *NO, enabling concurrent coupling and hydrogenation. This results in a Faradaic efficiency of 67.25 ± 3.27% and a urea production rate of 21.02 ± 0.83 mmol g –1 h –1 on pure Cu in 0.1 M KHCO 3 at −0.5 V vs RHE─surpassing all previous Cu-based systems. Our work identifies a more efficient one-step C–N coupling mechanism through simple electrolyte modulation.