Electron Deficiency is More Important than Conductivity in C-N Coupling for Electrocatalytic Urea Synthesis

The electrocatalytic C-N coupling from CO2 and nitrate emerges as one of the solutions for waste upgrading and urea synthesis. In this work, we constructed electron-deficient Cu sites by the strong metal-polymer semiconductor interaction, to boost efficient and durable urea synthesis. In situ Raman spectroscopy identified the existence of electron-deficient Cu sites and was able to withstand electrochemical reduction conditions. Operando synchrotron-radiation Fourier transform infrared spectroscopy and theoretical calculations disclosed the vital role of electron-deficient Cu in adsorption and C-N coupling of oxygen-containing species. The electron-deficient Cu displayed a high urea yield rate of 255.0 mmol h-1 g-1 at -1.4 V versus the reversible hydrogen electrode and excellent electrochemical durability, superior than that of non-electron-deficient counterpart with conductive carbon material as the support. It can be concluded that the regulation of site electronic structure is more important than the optimization of catalyst conductive properties in the C-N coupling reactions.