Electrocatalytic CO2 Upgrading to Triethanolamine by Bromine‐assisted C2H4 Oxidation

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 (C-n>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 Br-2 over *O or Cl-2 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.