Alkyl sulfonate surfactant mediates electroreduction of carbon dioxide to ethylene or ethanol over hydroxide-derived copper catalysts.

For CO 2 electroreduction (CO 2 ER) to C 2 compounds, it is generally accepted that the formation of ethylene and ethanol shares the same intermediate, *HCCOH. The majority of studies have achieved high faradaic efficiency (FE) towards ethylene, but faced challenges to get high ethanol FE. Herein, we present an alkyl sulfonate surfactant ( e.g. , sodium dodecyl sulfonate, SDS) mediated CO 2 ER to a C 2 product over an in situ generated Cu catalyst (Cu@SDS) from SDS-modified Cu(OH) 2 . It achieves the CO 2 ER to ethylene as the sole C 2 product at low applied voltages with a FE of 55% at -0.6 V vs. RHE and to ethanol as the main product at potentials ≥0.7 V with a maximum FE of 64% and a total C 2 FE of 86% at -0.8 V, with a current density of 231 mA cm -2 in a flow cell. Mechanism investigation indicates that SDS modifies the oxidation state of the in situ formed Cu species in Cu@SDS, thus tuning the catalyst activity for CO 2 ER and lowering the C-C coupling energy barrier; meanwhile, it tunes the adsorption mode of the *HCCOH intermediates on the catalyst, thus mediating the selectivity of CO 2 ER towards C 2 products.