Chaotropic Anions Promote Electrochemical C-C Bond Formation by Reshaping Interfacial Solvation

Area of Science:

• Electrochemistry
• Physical Chemistry
• Chemical Biology

Background:

• Anions are known to influence carbon monoxide (CO) and carbon dioxide (CO2) electroreduction.
• The precise mechanisms controlling this influence remain incompletely understood.
• The Hofmeister series provides a framework for understanding ion effects on water structure and protein solubility.

Purpose of the Study:

• To investigate the role of anions in CO2 electroreduction.
• To elucidate the mechanism by which anions affect reactivity through interfacial solvation.
• To correlate anion properties with the formation of multicarbon products.

Main Methods:

• Examined four anions (acetate, chloride, triflate, perchlorate) representing a spectrum of chaotropic and kosmotropic properties.
• Performed electrochemical measurements to quantify product formation and current density.
• Utilized in situ Raman spectroscopy and temperature-dependent measurements to probe interfacial water structure and reaction kinetics.

Main Results:

• Perchlorate, a highly chaotropic anion, enhanced C2+ product formation by 3.7 times compared to acetate.
• Achieved a high total current density of -782 ± 34 mA cm-2 at -1.50 V versus the Normal Hydrogen Electrode with perchlorate.
• Chaotropic anions were found to increase activation entropy, indicating greater interfacial water disorder.

Conclusions:

• Anion-driven water structuring is a critical factor in CO2 electroreduction.
• Modulating interfacial solvation through anion selection offers a powerful strategy to enhance multicarbon product selectivity and yield.
• This work provides a mechanistic link between the Hofmeister effect and electrochemical reactivity.