Tandem Catalysis on Phase-Separating Alloys for Electrochemical Urea Synthesis

In this work, density functional theory calculations combined with a constant-potential model are used to examine urea formation by co-reduction of CO 2 and NO 3 – on Co(111), Ni(111), Cu(111), and Zn(0001) surfaces, representing metals with distinct N and O adsorption characteristics. While Cu and Zn both promote C–N coupling, each surface exhibits thermodynamic limitations in different elementary steps. These complementary roles motivate a phase-separating Cu–Zn tandem catalyst in which NO 3 – adsorption and the first C–N coupling occur on Zn to form *NH 2 COOH, followed by spillover to Cu for subsequent hydrogenation and the final C–N coupling. Guided by the resulting empirical criterion that metals with higher O-affinity than N-affinity and moderate N adsorption favor C–N coupling, the screening is extended to the full transition-metal series, identifying Cu, Zn, Ag, and Cd as viable components and yielding six candidate tandem combinations. This work establishes a phase-separating tandem catalysis framework and offers transferable guidance for catalyst design in electrochemical urea synthesis.