Tuning C─N Coupling Mode by Cu─In Dual Metal Sites in Covalent Organic Framework for Enhanced Urea Electrosynthesis
Nan Wang, Yuan Zhang, Chunfeng Shao, Lei Yuan, Mingming Sun, Huiyong Wang, Suojiang Zhang, Jianji Wang
Abstract
Abstract Electrochemical conversion of CO 2 and NO 3 − to high value‐added urea is a win–win strategy for both resources and the environment. However, the yield rate and selectivity of urea are still low. In this work, Cu and In metals are grafted into the interlayers of an imine‐linked covalent organic framework (COF) to form stable Cu─In dual metal sites by strong coordination of hydroxyl O and imine N atoms in the framework. It is found that the optimal CuIn 1.07 ‐COF electrocatalyst exhibits an impressive urea yield rate of 2924.4 µg h −1 mg −1 and high Faradaic efficiency (FE) of 54.7% in H‐cell, which surpasses that of most previously reported catalysts for urea electrosynthesis. In situ spectroscopy and theoretical calculations reveal that due to the stronger electronic interaction between Cu and In, * NH 2 intermediate is generated on the In site from NO 3 − reduction, and then couples with * CO 2 on neighbor Cu site to produce * CO 2 NH 2 with a lower energy barrier, which effectively promotes the electrochemical co‐reduction of CO 2 and NO 3 − to urea. The work provides new clues for understanding the structure‐performance relationship in urea electrosynthesis.