Brass Phase Determining Selectivity in Urea Electrosynthesis from CO₂ and Nitrate

Urea synthesis using CO2 and nitrate (NO3–) co-electrolysis represents an alternative to the traditional thermochemical Bosch–Meiser protocol, although the yield rate remains low. The design of a bicomponent catalyst should prioritize because intermediates engaged in co-electrolysis are energetically favorable on distinct segments. Investigations into the component configuration at the atomic level are still lacking. Given the differences in activation kinetics and stoichiometry of CO2 and NO3– needed for urea synthesis, we use two-phase CuZn alloys (known as brass) with varying atomic ratios and configurations to demonstrate the role of phase engineering in determining the urea selectivity via CO2 and NO3– co-electrolysis. α-phase brass with an unbalanced CuZn atomic ratio and disordered atomic arrangement exhibits favored electronic structures with modest *NO2 adsorption and facilitated *CO2 activation, leading to efficient C–N coupling to form key *CO2NO2 intermediates. In contrast, ordered intermetallic β-CuZn shows excessive *NO2 adsorption, resulting in a further reduction. Accordingly, α-CuZn exhibits a high Faradaic efficiency of 28.7% and yield rate of 60.0 mmol h–1 g–1 in flow cells, outperforming that of β-CuZn. This study highlights the relevance of atomic scale and arrangement in co-electrolysis, which involves the coupling of distinct reaction kinetics and requires varied stoichiometry.