Optimizing the electronic structure of copper and cobalt dual sites for efficient electrosynthesis of urea

Abstract

The construction of dual catalytic sites to regulate the adsorption and activation of CO₂ and NO₃⁻ is critically important for the selective electrosynthesis of urea. Here, we report a CuCo alloy nanoparticle-encapsulated N-doped carbon nanotube (CuCo@N-CNT) catalyst for efficient and selective electrosynthesis of urea. The results demonstrated that the carbon nanotubes and the molar ratio of Cu to Co have a key influence on the surface electronic structure of CuCo@N-CNTs, thus effectively regulating the adsorption and activation of CO₂ and NO₃⁻ to obtain high-efficiency urea synthesis. As a result, the fabricated Cu₁Co₁@N-CNTs exhibited the highest urea yield of 3489.01 ± 34.35 μg h⁻¹ mg_cat⁻¹ with a faradaic efficiency of 73.69 ± 1.83% at −0.8 V (vs. RHE). The in situ spectroscopy and mass spectrometry measurements revealed that the first C–N coupling reaction involves the generation of *CONH₂ species through *CO and *NH₂ originated from the co-reduction of CO₂ and NO₃⁻ on Cu₁Co₁@N-CNTs. This can be further supported by theoretical calculation results. Furthermore, competitive side reactions such as CO₂ reduction, H₂ evolution and NO₃⁻ reduction can be effectively suppressed by modulating the position of the d-band centre of CuCo alloy nanoparticles, promoting the electrosynthesis of urea.