Tailoring the triple-phase microenvironment for kinetically matched C-N coupling in urea electrosynthesis

Urea synthesis by co-electroreduction of CO 2 and nitrate provides a promising strategy for sustainable fertilizer production. Despite advances in catalyst exploration, it is of significance to figure out the microenvironment on the electrode interface toward the kinetically matched C-N coupling. Here, we fabricated a hydrophobic triple-phase catalytic interface through a simply blending of commercial CuZn alloy and polytetrafluoroethylene (PTFE) particles for proof of concept. Incorporating PTFE boosted the Faradaic efficiency of urea from 8 % to 49 % and tripled the urea production rate. Kinetics and in-situ spectra studies reveal that hydrophobicity slows the proton/electron transfer during nitrate reduction, accelerates CO₂ diffusion at the triple-phase interface, and preserves high-valent asymmetric adsorption sites. This synergy extends the lifetime and surface coverage of critical C-/N-intermediates, and thus kinetically-matched asymmetric C-N coupling. Low catalytic selectivity incurred by kinetically mismatched electroreduction of C- and N-source, and hence inefficient chemical C-N coupling is the major limitation for urea electrosynthesis. Here, we investigated the hydrophobicity effect on the triple-phase interface upon urea electrosynthesis, and found that a hydrophobic interface promotes gas diffusion as well as decelerates the electro-hydrogenation of N-source, which balances the kinetically matched electrochemical C-N coupling process. • Hydrophobic microenvironment impacts the kinetic matching during the C-N coupling. • Hydrophobicity influences proton/electron transfer processes for NO 3 RR and CO 2 diffusion for CO 2 RR. • The kinetics of CO 2 -to-*CO and NO 3 - -to-*NH 2 can thus be simultaneously tuned on the hydrophobic interface. • FE urea can be greatly improved from 8 % to 49 % by adding 40 % PTFE to the CuZn catalyst.