Nanoporous Copper for the Electrosynthesisof Cyclic Carbonates from CO₂ and Epoxides

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.