Cobalt phthalocyanine-based conjugated polymer as efficient and exclusive electrocatalyst for CO2 reduction to ethanol

Abstract

Electrocatalytic conversion of carbon dioxide to high value-added chemicals is a promising method for solving the energy crisis and global warming. Electrochemical active metal-containing conjugated polymers have been widely studied for heterogeneous carbon dioxide reduction. In the present contribution, we designed and synthesized a stable cobalt phthalocyanine-based conjugated polymer, named CoPPc-TFPPy-CP, and also explored its electrocatalytic application in carbon dioxide reduction to liquid products in an aqueous solution. In the catalyst, cobalt phthalocyanine acts as building blocks connected with 1,3,6,8-tetrakis(4-formyl phenyl)pyrenes via imine-linkages, leading to mesoporous formation polymers with the pore size centered at 4.1 nm. And the central cobalt atoms shifted to a higher oxidation state after condensation. With these chemical and structural natures, the catalyst displayed a remarkable electrocatalytic CO₂ reduction performance with an ethanol Faradaic efficiency of 43.25% at −1.0 V vs RHE. While at the same time, the electrochemical reduction process catalyzed by cobalt phthalocyanine produced only carbon monoxide and hydrogen. To the best of our knowledge, CoPPc-TFPPy-CP is the first example among organic polymers and metal-organic frameworks that produces ethanol from CO₂ with a remarkable selectivity.