Crystalline Copper(II) Phthalocyanine Catalysts for Electrochemical Reduction of Carbon Dioxide in Aqueous Media

We achieved highly selective electrochemical reduction of CO 2 to C 2 H 4 (faradaic efficiency of 25%) by crystalline copper phthalocyanine (CuPc) supported on carbon black. Remarkably, noncrystalline CuPc generated by treatment of crystalline CuPc with sulfuric acid did not give C 2 H 4 selectively, suggesting that catalyst crystallinity is crucial for the selective conversion of CO 2 to C 2 H 4 . The stability of crystalline CuPc under electrochemical reduction conditions was also evaluated, showing that crystalline CuPc can selectively convert CO to C 2 H 4 in the initial stage (<10 000 s), as long as the crystallinity of the catalyst is maintained.