Spectroelectrochemical insight into copper cobalt catalysts for CO₂ and nitrite co-electroreduction to urea.

Abstract

Electrochemical CO₂ and nitrite co-reduction provides a sustainable urea synthesis route but remains limited by low selectivity and an undecided C-N coupling mechanism. Here, we report co-sputtered bimetallic Cu-Co catalysts that facilitate urea formation via a tandem relay mechanism. The optimal Cu:Co ratio of 1:1 achieves a urea yield rate of 61 ± 6 mmol h⁻¹g_cat⁻¹ at -1.2 V vs. RHE under neutral pH, emphasizing the importance of proton balance in sustaining proton-coupled electron transfer. In situ synchrotron-based infrared and Raman spectroscopy monitor the dynamic evolution of *CO, *NH₂, and C‒N intermediates. In situ X-ray absorption spectroscopy indicates the structural stability of metallic Cu and Co active sites. Density functional theory calculations suggest that *COOH + *NH₂ coupling initiates urea pathway, with *NH₂CO formation as the potential-determining step. This study integrates rational catalyst design and in situ spectroelectrochemical analysis to advance understanding of electrochemical C-N coupling for urea synthesis.