Electrocatalytic CO2 Upgrading to Triethanolamine by Bromine‐Assisted C2H4 Oxidation

Abstract The electrocatalytic carbon dioxide (CO 2 ) 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 (C 2 H 4 ), a major CO 2 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 CO 2 electrolysis cell for in situ C 2 H 4 generation and a C 2 H 4 oxidation/nitrite reduction cell, the capability of upgrading of CO 2 and nitrite into triethanolamine was demonstrated.