Nanoporous Copper for the Electrosynthesisof Cyclic Carbonates from CO2 and Epoxides

Abstract

Cyclic carbonates are often produced through catalytic coupling reactions of CO2 with epoxides under harsh conditions. Here, we present a highly active nanoporous copper (np-Cu) cathode material for the electrosynthesis of cyclic carbonates in mild environments. Np−Cu material was drop casted on glassy carbon (np-Cu/GC) as cathode electrode to perform galvanostatic electrosynthesis using a magnesium anode in CO2-saturated acetonitrile with 0.1 M tetraethylammonium iodide. Very good yields have been obtained for 1,2-butylene carbonate (BC, 74 ± 4 %) and propylene carbonate (PC, 62 ± 6 %). By varying the cathode electrode materials, low yields (≤ 20 %) on bare GC, but similar yields (76 ± 4 % BC and 63 ± 5 % PC) on polycrystalline Cu were achieved. Although the pore-ligament structure is beneficial to enhance the CO2RR performance, its impact on the yield of cyclic carbonate is minimal. This implies that the activation of CO2 to the CO2⋅− radical anion is not the rate-limiting step, but rather the ring closure of the final intermediate to form cyclic carbonates. Moreover, the np-Cu/GC shows very good stability and reusability for the electrochemical-organic test reaction. This study provides deeper insights into the reaction mechanism of cyclic carbonates formation on Cu-based electrodes.