CuZn nanoalloy encapsulated within tannic acid-functionalized carbon nanotubes for efficient electrocatalytic urea synthesis

Abstract

Electrocatalytic C–N coupling of carbon dioxide (CO₂) and nitrate (NO₃⁻) is regarded as an energy-efficient and sustainable strategy for urea production. However, this reaction involves multiple electron-transfer processes and complex intermediates. In particular, the CO₂ reduction reaction (CO₂RR) generally requires a higher overpotential than the nitrate reduction reaction (NtrRR), which severely hinders the formation of the target product. To address this challenge, we designed a CuZn nanoalloy encapsulated within carbon nanotubes (CNTs) and further coated with tannic acid (TA). The hydroxyl groups of TA establish noncovalent interactions with CO₂, thereby enhancing its adsorption, while the synergistic effect between Cu and Zn inhibits the NtrRR and facilitates the co-reduction of CO₂ and NO₃⁻. As a result, the catalyst achieves a maximum urea yield of 887.48 µg mg_cat.⁻¹ h⁻¹ with a faradaic efficiency of 47.2% at −0.8 V vs. RHE. Comprehensive product analysis coupled with in situ spectroscopic studies reveals that the cooperative interaction between Cu and Zn suppresses the over-reduction of NO₃⁻, promotes the effective activation of CO₂ and free water, and accelerates the coupling of *NH₂ and *CO intermediates into *CONH₂, thereby enabling efficient urea synthesis. This work highlights that CNT-encapsulated nanoalloy electrocatalysts provide valuable insights for the sustainable and efficient production of C–N compounds.