A bio-inspired O-tolerant catalytic CO reduction electrode.

The electrochemical reduction of CO to give CO in the presence of O would allow the direct valorization of flue gases from fossil fuel combustion and of CO captured from air. However, it is a challenging task because O reduction is thermodynamically favored over that of CO. 5% O in CO near catalyst surface is sufficient to completely inhibit the CO reduction reaction. Here we report an O-tolerant catalytic CO 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 CO reduction to CO coated with a polymer of intrinsic microporosity that works as a CO-selective layer with a CO/O selectivity of ∼20. Integrated into a flow electrolytic cell, the hybrid electrode operating with a CO feed gas containing 5% O exhibits a FE of 75.9% with a total current density of 27.3 mA/cm at a cell voltage of 3.1 V. A FE of 49.7% can be retained when the O fraction increases to 20%. Stable operation for 18 h is demonstrated. The electrochemical performance and O tolerance can be further enhanced by introducing cyano and nitro substituents to the phthalocyanine ligand.