Polycation-functionalized interface enable in situ capturing of CO2 and filtering of proton for efficient C-N coupling toward highly selective urea electrosynthesis

Electrochemical co-reduction of CO2 and nitrate provides a novel route to convert waste emissions into value-added chemicals such as urea. However, at the actual reaction interface, the insufficient supply of CO2 reactants as well as the excessive coverage of proton and nitrate on the electrocatalyst surface usually lead to complex product distributions from individual hydrogen evolution or nitrate reduction as side reactions, instead of C-N coupling. Here, we rationally optimize this interface by polycation functionalization, forcing highly selective urea electrosynthesis. The abundant polyamine nodes within the functional layer are conductive to in situ capturing of CO2 and filtering of proton, which pertinently control the reagent concentration to promote the selective C-N coupling and inhibit the undesired side reactions. When this tailored interface is coupled with efficient electrocatalyst with neighboring active sites, the proof-of-concept system delivers a maximum urea generation yield rate of 1254.2 μg h−1 mg−1 along with a Faradaic efficiency of 83.4 %, as well as outstanding Nurea-selectivity of 91.3 % and Curea-selectivity of nearly 100 %, which is one of the most selective urea generation systems reported so far. This work provides new insights in regulating the catalysis microenvironment for the improvement of overall performance in electrochemical C-N coupling.