Electrocatalytic CO2 Upgrading to Triethanolamine by Bromine‐Assisted C2H4 Oxidation

• Published in: Angewandte Chemie Vol. 135; no. 5
• Main Authors: Wang, Qihao, Yang, Chao, Yan, Yaqin, Yu, Haisheng, Guan, Anxiang, Kan, Miao, Zhang, Quan, Zhang, Linjuan, Zheng, Gengfeng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 26.01.2023
• Subjects: Ammonia; Bromine; Bromine Evolution Reaction; Carbon dioxide; Catalysts; Chemistry; CO2 Electroreduction; Coupling; Electrocatalysis; Electrolysis; Ethylene Oxidation; Greenhouse gases; Metal Phthalocyanine; Metal phthalocyanines; Molecular chains; Nitrites; Oxidation; Triethanolamine
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202212733

The electrocatalytic carbon dioxide (CO2) reduction is a promising approach for converting this greenhouse gas into value‐added chemicals, while the capability of producing products with longer carbon chains (Cn>3) is limited. Herein, we demonstrate the Br‐assisted electrocatalytic oxidation of ethylene (C2H4), a major CO2 electroreduction product, into 2‐bromoethanol by electro‐generated bromine on metal phthalocyanine catalysts. Due to the preferential formation of Br2 over *O or Cl2 to activate the C=C bond, a high partial current density of producing 2‐bromoethanol (46.6 mA⋅cm−2) was obtained with 87.2 % Faradaic efficiency. Further coupling with the electrocatalytic nitrite reduction to ammonia at the cathode allowed the production of triethanolamine with six carbon atoms. Moreover, by coupling a CO2 electrolysis cell for in situ C2H4 generation and a C2H4 oxidation/nitrite reduction cell, the capability of upgrading of CO2 and nitrite into triethanolamine was demonstrated. A CO2 upgrading strategy was developed by using Br‐assisted C2H4 oxidation, which exploits the preferential adsorption of *Br over *OH on metal phthalocyanine electrocatalysts. The C2H4 oxidation was further coupled with the nitrite reduction to form triethanolamine. Using two electrolysis cells in tandem, the capability of electrochemical fixation of CO2 and nitrite ions into triethanolamine at ambient conditions was demonstrated.