Interfacial modification of Zn foil electrode with cationic surfactants enables efficient and selective CO production from CO2 electroreduction

Abstract

Modification of interfacial properties of the electrode/electrolyte (E/E) offers an ability to effectively tune the activity and selectivity of metal electrodes towards electrocatalytic CO₂ reduction reaction (CO₂RR) but remains challenging. Herein, we demonstrate that directly introducing cationic surfactants with long-alkaryl chains in electrolyte can greatly promote the CO₂RR on Zn foil electrode. With addition of cetyltrimethylammonium bromide (CTAB) in 0.1 M KHCO₃ solution, the Zn foil electrode presents a maximum CO Faradaic efficiency (FE_CO) of 94.3% with a CO current density (j_CO) of 4.9 mA cm⁻² at −0.90 V vs. reversible hydrogen electrode (RHE), much superior to those of the Zn foil electrode in the same electrolyte without CTAB (FE_CO = 22.5% and j_CO = 0.48 mA cm⁻² at −0.91 V vs. RHE), and the enhanced j_CO and FE_CO are maintained over a period of 8 h electrolysis. The enhanced CO₂RR efficiency can be attributable to the dynamic adsorption of positively charged long-alkaryl chains on the polarized Zn foil electrode that can promote the CO₂ penetration and adsorption to the active sites while suppressing the competing H₂ evolution reaction (HER). Density functional theory (DFT) calculations reveal that the CTAB-modified E/E interface can significantly reduce the energy barrier of *CO desorption, thus enhancing the efficiency of CO₂ reduction to CO.