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 (Cn >3) is limited. Herein, we demonstrate the Br-assisted electrocatalytic oxidation of ethylene (C2 H4 ), 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 C2 H4 generation and a C2 H4 oxidation/nitrite reduction cell, the capability of upgrading of CO2 and nitrite into triethanolamine was demonstrated.