Improving the lifetime of hybrid CoPc@MWCNT catalysts for selective electrochemical CO2-to-CO conversion

Molecular hybrid catalysts, such as cobalt(II) phthalocyanine (CoPc) complexes anchored to multi-walled carbon nanotubes (MWCNTs), provide selective CO2 conversion toward CO with high current densities, exceeding 0.1 A cm(-2) in microfluidic or zero-gap (membrane) electrolyzers. However, the practicality of CO2 electroreduction is essentially determined by the catalyst stability against mechanical and (elec-tro)chemical degradation. Here, we report a new mechanism for the observable degradation of the CoPc@MWCNT hybrid catalyst. Even at moderate CO2 reduction potentials, the demetalation of CoPc complexes is induced by a reduction of iron (Fe) species, which can contaminate commercially available MWCNTs or solvents used for catalyst preparation. Minimization of Fe contamination leads to a substan-tial improvement in the CoPc@MWCNT catalyst lifetime, with the faradaic efficiency of CO formation decreasing from 98% to 96% (by only 2%) after 95 hof electrolysis. Thus, careful purification of hybrid cat-alyst materials is required to maintain initial levels of catalyst performance during long-term operation.(c) 2022 The Author(s). Published by Elsevier Inc.This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

The stability of cobalt phthalocyanine (CoPc) complexes in CO2 electroreduction is affected by mechanical and chemical degradation. Iron contamination causes the observable degradation of the CoPc@MWCNT hybrid catalyst. Therefore, careful purification of catalyst materials is necessary to maintain catalyst performance.