Selective nitrogen fixation via Janus C-N coupling in co-electrolysis

Summary

Electrocatalysis offers a sustainable approach to artificial nitrogen fixation yet faces numerous challenges. Selective synthesis of nitrogen-containing compounds shows promise but needs significant improvement. Herein, we demonstrate selective ammonia and urea synthesis via co-electrolysis with CO₂. High CO binding energy on Re-Mn catalysts leads to the formation of ∗C species, which serve as electron reservoirs to enhance N₂ activation for C-N coupling (N₂ + ∗C → ∗CN₂), followed by C-N dissociation. This results in ammonia production with a yield rate of 48.9 ± 2.4 mg g⁻¹ h⁻¹ and an N-selectivity of 98.4%. In contrast, Zn-Mn sites, characterized by low CO binding, facilitate the migration of CO and its coupling with adsorbed N₂ (CO + ∗N=N∗ → ∗NCON∗). Subsequent hydrogenations of ∗NCON∗ promote urea synthesis with an N-selectivity of 89.1%. Utilizing Janus coupling with two C-N pathways aims to meet energy, agriculture, and chemical industry demands. We realized the selective synthesis of ammonia and urea, respectively, in one electrocatalytic system for the first time by Janus coupling with two distinguishable C-N coupling paths from N₂ and CO₂.