CO(2) Reduction Selective for C(≥2) Products on Polycrystalline Copper with N-Substituted Pyridinium Additives

[Image: see text] Electrocatalytic CO(2) reduction to generate multicarbon products is of interest for applications in artificial photosynthetic schemes. This is a particularly attractive goal for CO(2) reduction by copper electrodes, where a broad range of hydrocarbon products can be generated but where selectivity for C–C coupled products relative to CH(4) and H(2) remains an impediment. Herein we report a simple yet highly selective catalytic system for CO(2) reduction to C(≥2) hydrocarbons on a polycrystalline Cu electrode in bicarbonate aqueous solution that uses N-substituted pyridinium additives. Selectivities of 70–80% for C(2) and C(3) products with a hydrocarbon ratio of C(≥2)/CH(4) significantly greater than 100 have been observed with several additives. (13)C-labeling studies verify CO(2) to be the sole carbon source in the C(≥2) hydrocarbons produced. Upon electroreduction, the N-substituted pyridinium additives lead to film deposition on the Cu electrode, identified in one case as the reductive coupling product of N-arylpyridinium. Product selectivity can also be tuned from C(≥2) species to H(2) (∼90%) while suppressing methane with certain N-heterocyclic additives.