Modifying the composition of the interfacial liquid, the region in contact with a charged solid, has emerged as a complementary strategy to enhance CO₂ electroconversion kinetics by creating a more favorable catalytic environment. This can be accomplished by using hydrophobic cation additives like the cetyltrimethylammonium. Here, we demonstrate that the enhancement effects of cetyltrimethylammonium are highly confined to undercoordinated metal sites.