Highly Efficient Electrosynthesis of Urea from CO<sub>2</sub> and Nitrate by a Metal–Organic Framework with Dual Active Sites
Xiaofeng Qiu, Jia‐Run Huang, Can Yu, Xiao‐Ming Chen, Pei‐Qin Liao
Abstract
Abstract Electrosynthesis of urea from CO 2 and NO 3 − is a sustainable alternative to energy‐intensive industrial processes. The main challenge hindering the progress of this technology lies in the development of advanced electrocatalysts that efficiently utilize abundant, low‐cost CO 2 and nitrogen sources to yield urea with both high Faradaic efficiency (FE) and current density. In this work, we designed and prepared a new two‐dimensional metal–organic framework (MOF), namely PcNi−Fe−O , constructed by nickel‐phthalocyanine (NiPc) ligands and square‐planar FeO 4 nodes, as the electrocatalyst for urea electrosynthesis. PcNi−Fe−O exhibits remarkable performance to yield urea at a high current density of 10.1 mA cm −2 with a high FE(urea) of 54.1 % in a neutral aqueous solution, surpassing those of most reported electrocatalysts. No obvious performance degradation was observed over 20 hours of continuous operation at the current density of 10.1 mA cm −2 . By expanding the electrode area to 25 cm 2 and operating for 8 hours, we obtained 0.164 g of high‐purity urea, underscoring its potential for industrial applications. Mechanism study unveiled the enhanced performance might be ascribed to the synergistic interaction between NiPc and FeO 4 sites. Specifically, NH 3 produced at the FeO 4 site can efficiently migrate and couple with the *NHCOOH intermediate adsorbed on the urea‐producing site (NiPc). This synergistic effect results in a lower energy barrier for C−N bond formation than those of the reported catalysts with single active sites.