CO_2 Reduction Selective for C_(≥2) Products on Polycrystalline Copper with N-Substituted Pyridinium Additives

Abstract

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)/CH4significantly 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.

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