Modulating the Electrode–Electrolyte Interface with Cationic Surfactants in Carbon Dioxide Reduction

Abstract

Copper is among the most studied electrocatalyst for CO2 conversion due to its remarkable ability to form high-order carbon products. However, controlling factors that lead to high carbon product selectivity remains a major hurdle to fundamental scientific understanding. In this work, we investigate the utility of cationic surfactants to modify the selectivity of Cu foil in electrocatalytic CO2 reduction (CO2RR). We demonstrate that cetyltrimethylammonium bromide (CTAB) significantly suppresses the hydrogen evolution reaction (HER), a competitive parallel reaction to CO2RR. In addition, high surfactant concentrations and long alkyl chain lengths enhance the selectivity for CO2RR in NaHCO3 solutions. Importantly, electrochemical impedance spectroscopy is used to monitor the evolution of the electrode–electrolyte interface in the presence of CTAB under varying experimental conditions. On the basis of our extensive electrochemical characterization, we propose that cationic surfactants accumulate in the electrochemical double layer and effectively lower the available proton sources for HER. Our approach provides a facile strategy to modify the surface reactivity of metal electrodes with broad implications for electrocatalysis.

Catalyst–Electrolyte Interactions in Aqueous Reline Solutions for Highly Selective Electrochemical CO2 Reduction

“…The pseudo‐capacitances in Figure A determined from electrochemical impedance spectroscopy (EIS, details including Nyquist plots and fitting results are included in the Supporting Information: Figure S7, Table S3, and Table S4) show that adding up to 1.47 g L −1 of ChCl to 0.5 m KHCO 3 reduces the specific capacitance from 60.54 to 46.14 μF cm −2 , and then remains steady at higher ChCl concentrations. The choline ions (Ch + ) are larger than K + ions, and higher Ch + concentrations reduce the dielectric constant and thus reduce capacitance . Therefore, we propose in Figure B that Ch + ions disrupt the DL formed by hydrated K + ions.…”

Electrochemical Production of Formic Acid from CO2 with Cetyltrimethylammonium Bromide‐Assisted Copper‐Based Catalysts

“…By comparison of the curves in Figures 4b and 2b, it can be easily deduced that the variation trends of the three products (CO, HCOOH, and H 2 ) are very similar. Especially, the tendency is almost the same when the potential is lower than −1.4 V (vs. SCE), suggesting that CTAB addition into the electrolyte can significantly improve HCOOH selectivity along with the distinct inhibition of the HER [12] …”

Unveiling the Synergistic Effect between Graphitic Carbon Nitride and Cu2O toward CO2Electroreduction to C2H4

“…In general, the main gaseous products of the CO 2 RR were CO, CH 4 and C 2 H 4 for these three catalysts. The hydrogen evolution reaction (HER) is a competitive reaction of CO 2 RR due to the faster water splitting kinetics [20] . In this paper, for convenience, we abbreviated the FE of C 2 H 4 , CH 4 , H 2 and CO to FE , FE , FE , FE CO , respectively.…”