A bio-inspired O2-tolerant catalytic CO2 reduction electrode

The electrochemical reduction of CO2 to give CO in the presence of O-2 would allow the direct valorization of flue gases from fossil fuel combustion and of CO2 captured from air. However, it is a challenging task because O-2 reduction is thermodynamically favored over that of CO2. 5% O-2 in CO2 near catalyst surface is sufficient to completely inhibit the CO2 reduction reaction. Here we report an O-2-tolerant catalytic CO2 reduction electrode inspired by part of the natural photosynthesis unit. The electrode comprises of heterogenized cobalt phthalocyanine molecules serving as the cathode catalyst with >95% Faradaic efficiency (FE) for CO2 reduction to CO coated with a polymer of intrinsic microporosity that works as a CO2-selective layer with a CO2/O-2 selectivity of similar to 20. Integrated into a flow electrolytic cell, the hybrid electrode operating with a CO2 feed gas containing 5% O-2 exhibits a FECO of 75.9% with a total current density of 27.3 mA/cm(2) at a cell voltage of 3.1 V. A FECO of 49.7% can be retained when the O-2 fraction increases to 20%. Stable operation for 18 h is demonstrated. The electrochemical performance and O-2 tolerance can be further enhanced by introducing cyano and nitro substituents to the phthalocyanine ligand. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.