Boosting Synergistic Catalysis C–N Coupling via Stabilizing Close Zn/Ti Bimetallic Sites for Electrocatalytic Urea Synthesis from CO2 and Nitrite

Abstract

Electrocatalytic urea synthesis is significantly limited by the low efficiency of C–N bond coupling between CO₂ and nitrite. Here, we designed a Zn and Ti bimetallic active site catalyst by anchoring TiO₂ on the surface of ZnO and developed a new NF@CoMn₂O₄@ZnO-TiO₂ electrocatalyst with high resistance to deactivation. The Co³⁺/Mn³⁺-Mn⁴⁺ solid oxide pairs in NF@CoMn₂O₄@ZnO-TiO₂ maintain their high stability by extracting accumulated electrons around Zn²⁺ and Ti⁴⁺ through strong electronic interactions. The Zn active sites on NF@CoMn₂O₄@ZnO-TiO₂ can efficiently catalyze the reduction of CO₂ to *CO, while the Ti active sites can efficiently catalyze the reduction of NO₂^– to the *NH₂ intermediate product. The proximity of the Zn and Ti sites shortens the coupling distance between the *CO and *NH₂ intermediates, facilitating the efficient electrocatalytic synthesis of urea. DFT calculations indicate that the ΔG required for the coupling of *CO and *NH₂ adsorbed on short-range Zn and Ti sites on CoMn₂O₄@ZnO-TiO₂ is lower compared to CoMn₂O₄@ZnO and ZnO. This results in a remarkably high Faradaic efficiency of 61.18% for urea synthesis at −0.6 V vs RHE for NF@CoMn₂O₄@ZnO-TiO₂. This work provides a new pathway for achieving synergistic catalysis of C–N coupling reactions between different metal catalytic sites.