Abstract: The electroreduction of CO2 and electrocatalytic synthesis of propylene carbonate (PC) were studied in dimethylformamide (DMF) solvent under mild conditions (p(CO2)=101 kPa, room temperature). CO2 can be electroreduced in DMF-0.1 mol/L tetraethylammonium bromide by cyclic voltammetry. An irreversible one-electron reduction peak of CO2 appeared at -2.1 V vs Ag, indicating that an activated species may be generated. The electrocatalytic synthesis of propylene carbonate from CO2 and propylene oxide in DMF was studied using six different supporting electrolytes. The results showed that supporting electrolytes including Br- acted as both a supporting electrolyte and a catalyst to synthesize propylene carbonate. The selectivity for propylene carbonate was 100%. A proposed mechanism involved the opening of the epoxide ring through a nucleophilic attack by Br-and Mg2+, which formed an intermediate affording propylene carbonate after reaction with the activated CO2.

Key words: carbon dioxide, propylene oxide, electrocatalytic synthesis, propylene carbonate, supporting electrolyte