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

Abstract

The direct electrochemical coupling of CO 2 and nitrate (NO 3 – ) 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 CO 2 and NO 3 – 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 0.9 S 2.9– x /Ag 2 S heterostructure catalyst, enabling the tandem coreduction of CO 2 and nitrate for urea electrosynthesis. Electrochemical studies, in situ 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 NO 3 – and CO 2 reduction. FeP 0.9 S 2.9– x offers a moderate conversion rate from NO 3 – to ammonia, generating *NH 2 intermediates while mitigating overhydrogenation to ammonia. Meanwhile, Ag 2 S with optimized loading facilitates efficient conversion of CO 2 to CO, enabling the diffusion and electrophilic attack of CO on *NH 2, thereby forming the critical *CONH 2 intermediate for urea production. As a result, the FeP 0.9 S 2.9– x /Ag 2 S 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 0.9 S 2.9 nanosheets and Ag 2 S 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.

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