Decoupled Control of CO₂ and Nitrate Reduction Intermediates to Enable Efficient Tandem Urea Electrosynthesis.

Abstract

The direct electrochemical coupling of CO₂ and nitrate (NO₃^-) offers a sustainable alternative to the energy-intensive Bosch-Meiser process for urea synthesis. However, achieving efficient C-N coupling at single active sites remains challenging due to the kinetic mismatch between CO₂ and NO₃^- reduction, as well as the intricate multistep proton-coupled electron transfer process. Here, we present a sacrificial template-based strategy to synthesize a two-dimensional (2D)/zero-dimensional (0D) FeP_0.9S_2.9-<i>x</i>/Ag₂S heterostructure catalyst, enabling the tandem coreduction of CO₂ and nitrate for urea electrosynthesis. Electrochemical studies, <i>in situ</i> measurements, and theoretical calculations together demonstrate that the heterostructures with strongly coupled interfaces not only modulate the electronic structure but also enable decoupled control over NO₃^- and CO₂ reduction. FeP_0.9S_2.9-<i>x</i> offers a moderate conversion rate from NO₃^- to ammonia, generating *NH₂ intermediates while mitigating overhydrogenation to ammonia. Meanwhile, Ag₂S with optimized loading facilitates efficient conversion of CO₂ to CO, enabling the diffusion and electrophilic attack of CO on *NH₂, thereby forming the critical *CONH₂ intermediate for urea production. As a result, the FeP_0.9S_2.9-<i>x</i>/Ag₂S tandem catalyst achieves a high urea yield rate of 1160.9 μg h^-1 mg_cat^-1 with a Faradaic efficiency (FE) of 15.4% at -0.7 vs reversible hydrogen electrode, outperforming the individual FeP_0.9S_2.9 nanosheets and Ag₂S nanoparticles. This study provides key insights into the rational design of heterostructure catalysts that exhibit strong interfacial interactions and allow for decoupled control over parallel reactions to enhance complex coupling processes.