CO₂Electroreduction in Water with a Heterogenized C-Substituted Nickel Cyclam Catalyst

Molecular catalysis for selective CO₂electroreduction into CO can be achieved with a variety of metal complexes. Their immobilization on cathodes is required for their practical implementation in electrolytic cells and can benefit from the advantages of a solid material such as easy separation of products and catalysts, efficient electron transfer to the catalyst, and high stability. However, this approach remains insufficiently explored up to now. Here, using an appropriate and original modification of the cyclam ligand, we report a novel [Ni(cyclam)]²⁺complex which can be immobilized on carbon nanotubes. This material, once deposited on a gas diffusion layer, provides a novel electrode which is remarkably selective for CO₂electroreduction to CO, not only in organic solvents but also, more remarkably, in water, with faradic efficiencies for CO larger than 90% and current densities of 5-10 mA cm^-2during controlled potential electrolysis in H-cells.