Co-Electrocatalytic Nitrate Reduction and Carbon Dioxide via a Nanobubble-Enhanced Membrane Electrode Assembly Electrolyzer

The practical application of electrocatalytic nitrate-to-ammonia conversion encounters an economic challenge, given that nitrate holds a higher market value than ammonia. To circumvent this limitation, we demonstrated a co-electrolysis strategy that converts nitrate and CO 2 into higher-value urea. Using a Cu-loaded ZrO 2 nanoframework (Cu/ZrO 2 NF) catalyst, selective C−N coupling was achieved between nitrate- and CO 2 -derived intermediates, reaching a urea yield rate of 459.31 μg·h −1 ·cm −2 at −0.9 V vs RHE with nearly 100% carbon selectivity. In situ Raman spectroscopy combined with theoretical calculations revealed that ZrO 2 supplied hydrogen radicals to facilitate protonation, while Cu sites mediated the coupling of *NH 2 and *CO. To overcome CO 2 mass-transfer constraints, a membrane electrode assembly (MEA) electrolyzer incorporating nanobubble dispersion was implemented, further increasing the yield rate of urea to 541.60 μg·h −1 ·cm −2, which is higher than that of many previously reported studies. A techno-economic analysis confirms the viability of the urea synthesis pathway, demonstrating its superior economic potential compared to standalone nitrate-to-ammonia conversion.