On-Surface Modification of Copper Cathodes by Copper(I)-Catalyzed Azide Alkyne Cycloaddition and CO(2) Reduction in Organic Environments

In this study, organic structures were introduced onto copper cathodes to induce changes in their electrocatalytic CO(2) reduction activity. Poorly soluble organic polymers were distributed onto the copper surface as a thin layer by polymerizing monomeric precursors via a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) activated by anodization of the copper substrate. The resulting structure possesses copper surface atoms that are available to participate in the CO(2) reduction reaction—comparable to close-contact organic structures—and stabilize the adsorption of organic layers through the CO(2) reduction process. The CO(2) reduction performance of the on-surface modified copper cathode exhibited improved CO(2) reduction over H(2) evolution compared with traditional cast modification systems. Preventing organic moieties from forming densely packed assemblies on the metal surface appears to be important to promote the CO(2) reduction process on the copper atoms. The suppression of H(2) evolution, a high methane/ethylene ratio, and the influence of stirring demonstrate that the improved CO(2) reduction activity is not only a result of the copper atom reorganization accompanied by repeating anodization for modification; the organic layer also apparently plays an important role in proton transfer and CO(2) accumulation onto the copper surface.