Achieving efficient urea electrosynthesis through improving the coverage of a crucial intermediate across a broad range of nitrate concentrations

Abstract

The electrocatalytic synthesis of urea by coupling of nitrate ions as a wastewater pollutant with CO₂ is a sustainable pathway. However, efficient electrosynthesis of urea across a broad range of nitrate concentrations has not been reported. Here, a series of Ru-doped Cu_xBi/CNT multisite catalysts for urea electrosynthesis are designed to benefit from triple synergistic modulation and exhibit excellent performance. The composition and ratio optimised Ru–Cu₉Bi/CNT catalyst achieves urea yields greater than 40.0 mmol h⁻¹ g⁻¹ over a wide range of nitrate concentrations (10–1000 mM) at −0.4 V vs. RHE. Notably, the highest FE value of 75.6% to date was achieved in 1 M nitrate solution. Comprehensive analysises show that the Cu and Bi sites activate CO₂ and NO₃⁻, respectively. In addition, doped Ru promotes water dissociation to form *H. In the key step of electrocatalytic urea synthesis, the strong adsorption of *H by doped Ru inhibits the hydrogen evolution reaction (HER). The acceleration of NO₃⁻ reduction by Bi synergises with the modulation of *H adsorption energy by Ru to improve the coverage of the key intermediate *NHO at different NO₃⁻ concentrations, ensuring the subsequent electrosynthesis of urea.