Cation-Induced Interfacial Hydrophobic Microenvironment Promotes the C–C Coupling in Electrochemical CO₂ Reduction

Abstract

The electrochemical carbon dioxide reduction reaction (CO 2 RR) toward C 2 products is a promising way for the clean energy economy. Modulating the structure of the electric double layer (EDL), especially the interfacial water and cation type, is a useful strategy to promote C−C coupling, but atomic understanding lags far behind the experimental observations. Herein, we investigate the combined effect of interfacial water and alkali metal cations on the C−C coupling at the Cu(100) electrode/electrolyte interface using ab initio molecular dynamics (AIMD) simulations with a constrained MD and slow-growth approach. We observe a linear correlation between the water-adsorbate stabilization effect, which manifests as hydrogen bonds, and the corresponding alleviation in the C−C coupling free energy. The role of a larger cation, compared to a smaller cation (e.g., K + vs Li + ), lies in its ability to approach the interface through desolvation and coordinates with the *CO+*CO moiety, partially substituting the hydrogen-bonding stabilizing effect of interfacial water. Although this only results in a marginal reduction of the energy barrier for C−C coupling, it creates a local hydrophobic environment with a scarcity of hydrogen bonds owing to its great ionic radius, impeding the hydrogen of surrounding interfacial water to approach the oxygen of the adsorbed *CO. This skillfully circumvents the further hydrogenation of *CO toward the C 1 pathway, serving as the predominant factor through which a larger cation facilitates C−C coupling. This study unveils a comprehensive atomic mechanism of the cation−water−adsorbate interactions that can facilitate the further optimization of the electrolyte and EDL for efficient C−C coupling in CO 2 RR.

Critical Role of Cu Nanoparticle-Loaded Cu(100) Surface Structures on Structured Copper-Based Catalysts in Boosting Ethanol Generation in CO2 Electroreduction

“…As shown in Table S2, the present Cu-F-M electrocatalyst exhibits better or comparable catalytic performance for the eCO 2 RR in terms of ethanol selectivity and current density in comparison to previously reported Cu-based electrocatalysts. In addition, as demonstrated in Figure S7b, after surface hydrophobic modification by sodium laurate, the hydrogen Faraday efficiency on Cu-F-M is reduced by more than 30% when compared to the Cu-F catalyst, attributable to the effective inhibition of the hydrogen evolution competition reaction by the hydrophobic surface, weakening the adsorption of *H, thereby enhancing the proportions of carbonic products (including ethanol) in the products of the eCO 2 RR. − Intriguingly, a small amount of n -propanol can be produced in the eCO 2 RR across all Cu-based electrocatalysts examined (Figure S7b,c), demonstrating the potential of present oxide-derived Cu-based electrocatalysts in transforming CO 2 into three-carbon products in the eCO 2 RR. , In addition, the Nyquist plots of Cu-based electrocatalysts (Figure S7d) reveal that the Cu-F-M catalyst has a medium charge transfer resistance among them. Furthermore, to eliminate the potential interference of surface-decorated sodium laurate on modified Cu-based electrocatalysts in the eCO 2 RR, a Cu-F-M catalyst was placed in an electrolyte containing 0.02 M sodium laurate.…”

Deciphering the role of aromatic cations in electrochemical CO2 reduction: interfacial ion assembly governs reaction pathways

“…This scenario is analogous to the formation of hydrophobic layers and the suppression of water reduction caused by organic coating or ion assembly on electrode surfaces in aqueous systems. 25,61,62…”

“…Indeed, there has been a resurgence in interest in studying how electrolyte properties also influence electrocatalytic reactions, 17–19 and many recent studies have shown that the properties of electrolytes can play at least an equally important role as electrodes in controlling reaction activity and selectivity. For instance, strategies such as increasing electrolyte pH, 20–23 changing the identity of supporting cations, 24–26 and decreasing water activity by increasing electrolyte concentration have been employed to enhance both the overall CO 2 conversion selectivity versus water reduction and the selective generation of multi-carbon products. 27…”

“…While electrode engineering primarily influences reaction pathways through changes in adsorbate binding energies, electrolytes can influence the electrocatalytic process through multiple mechanisms, including changes in interfacial electric field gradients, alterations to proton transport, and modification of thermodynamic activity of both products and reactants. 7,24–29 This multidimensional control enables distinct opportunities for studying and understanding electrochemical CO 2 reduction and promises to reveal new strategies for impacting other emerging electrocatalytic reactions, such as nitrate reduction and selective C–N bond formation.…”

Not One, Not Two, But at Least Three: Activity Origin of Copper Single-Atom Catalysts toward CO2/CO Electroreduction to C2+ Products

“…With the confirmation of the local coordination environment of Cu 1 , we then investigated its reaction process by focusing on two key steps, i.e., *CO → *CHO and CO–CO coupling. − *CHO formation on Cu 1 @C 3 N 4 through the Eley–Rideal (ER) mechanism is endothermic with an insurmountable E a of 1.81 eV. The adsorption of the second CO molecule on Cu 1 @C 3 N 4 is slightly endothermic (Figure c), and *CO coupling is unfavorable, given that its E a is 1.29 eV.…”