Carbon‐Nanotube‐Supported Copper Polyphthalocyanine for Efficient and Selective Electrocatalytic CO2 Reduction to CO

Electroreduction of CO2 to CO is one of the simplest ways to valorise CO2 as a source of carbon. Herein, a cheap, robust, Cu‐based hybrid catalyst consisting of a polymer of Cu phthalocyanine coated on carbon nanotubes, which proved to be selective for CO production (80 % faradaic yield) at relatively low overpotentials, was developed. Polymerisation of Cu phthalocyanine was shown to have a drastic effect on the selectivity of the reaction because molecular Cu phthalocyanine was instead selective for proton reduction under the same conditions. Although the material only showed isolated Cu sites in phthalocyanine‐like CuN4 coordination, in situ and operando X‐ray absorption spectroscopy showed that, under operating conditions, the Cu atoms were fully converted to Cu nanoparticles, which were likely the catalytically active species. Interestingly, this restructuring of the metal sites was reversible. Transient restructuring: A copper polyphthalocyanine/carbon nanotubes hybrid catalyst exhibits high selectivity for electroreduction of CO2 to CO. Operando X‐ray absorption spectroscopy shows reversible restructuring of the catalyst surface during electrolysis. At cathodic potentials, transient small Cu nanoparticles are formed and are likely the catalytically active species. The initial material with isolated Cu sites is recovered at anodic potentials.