Brass Phase Determining Selectivity in Urea Electrosynthesis from CO2 and Nitrate

Abstract

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.