Ligand engineering towards electrocatalytic urea synthesis on a molecular catalyst
Li Han, Leitao Xu, Shuowen Bo, Yujie Wang, Xu Han, Chen Chen, Ruping Miao, Dawei Chen, Kefan Zhang, Qinghua Liu, Jingjun Shen, Huaiyu Shao, Jianfeng Jia, Shuangyin Wang
Abstract
Electrocatalytic C-N coupling from carbon dioxide and nitrate provides a sustainable alternative to the conventional energy-intensive urea synthetic protocol, enabling wastes upgrading and value-added products synthesis. The design of efficient and stable electrocatalysts is vital to promote the development of electrocatalytic urea synthesis. In this work, copper phthalocyanine (CuPc) is adopted as a modeling catalyst toward urea synthesis owing to its accurate and adjustable active configurations. Combining experimental and theoretical studies, it can be observed that the intramolecular Cu-N coordination can be strengthened with optimization in electronic structure by amino substitution (CuPc-Amino) and the electrochemically induced demetallation is efficiently suppressed, serving as the origination of its excellent activity and stability. Compared to that of CuPc (the maximum urea yield rate of 39.9 ± 1.9 mmol h−1 g−1 with 67.4% of decay in 10 test cycles), a high rate of 103.1 ± 5.3 mmol h−1 g−1 and remarkable catalytic durability have been achieved on CuPc-Amino. Isotope-labelling operando electrochemical spectroscopy measurements are performed to disclose reaction mechanisms and validate the C-N coupling processes. This work proposes a unique scheme for the rational design of molecular electrocatalysts for urea synthesis. Electrocatalytic C-N coupling of carbon dioxide and nitrate offers a sustainable alternative to traditional urea production. Here the authors report amino substitution in copper phthalocyanine for enhanced urea electrosynthesis.