Enhanced Charge Transfer Kinetics for the Electroreduction of Carbon Dioxide on Silver Electrodes Functionalized with Cationic Surfactants

Abstract

Cationic ammonium surfactants can be used together with a suitable catalyst to enhance the electroreduction of carbon dioxide (CO2RR). However, the underlying reasons for the improvements are not yet well understood. In this work, it is shown that didodecyldimethylammonium bromide (DDAB; [(C12H25)2N(CH3)2]Br), when added to the catholyte, can increase the rate of CO2 reduction to CO on silver electrodes by 12-fold at −0.9 V versus reversible hydrogen electrode. More importantly, electrochemical impedance spectroscopy revealed that DDAB lowered the charge transfer resistance (RCT) for CO2RR on silver, and these changes can be correlated with enhancements in partial current densities of CO. Interestingly, when DDAB is added onto two other CO-producing metals, namely, zinc and gold, the CO2RR charge transfer kinetics are improved only on Zn, but not on Au electrodes. By means of a semiempirical model combining density functional theory calculations and experimental data, it is concluded that DDAB generally strengthens the adsorption energies of the *COOH intermediate, which leads to enhanced CO production on silver and zinc, but not on gold.