Dynamic Anionic Surfactant Assembly Induces Interfacial K⁺ Enrichment to Steer *CO Adsorption Configurations for Enhanced C-C Coupling in CO₂ Electroreduction.

Abstract

Electrochemical CO₂ reduction (CO₂RR) to multicarbon (C₂₊) products is essential for carbon neutrality, yet achieving high selectivity at industrial current densities remains challenging. While cationic and nonionic surfactants modulate the microenvironment, the role of anionic surfactants in C-C coupling is elusive. Herein, we present an interfacial engineering strategy using a phosphonic-acid-terminated anionic surfactant, tetradecylphosphonic acid (TDPA), on copper catalysts to achieve exceptional C₂₊ selectivity. <i>Operando</i> characterizations reveal a potential-driven transition of the TDPA layer from covalent chemisorption to electrostatic physisorption, inducing a 4-fold enrichment of localized K⁺ cations. <i>In-situ</i> vibrational spectroscopies and DFT calculations show that this concentrated K⁺ layer reconfigures *CO adsorption from predominantly bridge-bonded species to coexisting bridge- and top-bonded species, thereby lowering the C-C coupling barrier. Consequently, the TDPA system delivers ∼90% C₂₊ Faradaic efficiency at 600 mA cm^-2, highlighting the role of the anionic surfactant in regulating the local ion distribution and intermediate configuration for CO₂ electrolysis.