Electrolyte Structure Governs Formate Oxidation in Water-in-Salt Systems

Area of Science:

• Electrochemistry
• Physical Chemistry
• Materials Science

Background:

• Water-in-salt electrolytes offer unique properties for electrochemical applications.
• Understanding the interplay between electrolyte structure and catalytic activity is crucial for optimizing performance.

Purpose of the Study:

• To investigate the influence of reactant concentration and electrolyte structure on catalytic activity.
• To elucidate the mechanisms behind performance limitations and identify strategies for enhancement.

Main Methods:

• Formate oxidation reaction on platinum (Pt) electrodes.
• Molecular dynamics (MD) simulations and Nuclear Magnetic Resonance (NMR) spectroscopy.
• Scanning Electrochemical Microscopy (SEIRAS) for in-situ analysis.

Main Results:

• Formate oxidation currents plateau at high concentrations due to formate ion clustering, reduced conductivity, and impeded transport.
• Addition of chaotropic perchlorate anions disrupts clustering, increasing formate oxidation currents.
• Excessive perchlorate disrupts the hydrogen-bonding network, hindering proton transport, causing local acidification, and promoting CO poisoning.

Conclusions:

• Electrolyte bulk structure directly impacts catalytic activity at high reactant concentrations.
• Controlling ion clustering and hydrogen-bonding networks is key to enhancing catalytic performance.
• This study provides insights for designing advanced electrolytes for improved electrochemical processes.