Quantification of the Electrostatic Effect on Redox Potential by Positive Charges in a Catalyst Microenvironment

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Charged functional groups in the secondary coordination sphere (SCS) enhance electrocatalyst reactivity.
• Accurate electrocatalyst benchmarking relies on linear free-energy scaling relationships.
• Electrochemical redox potentials may be influenced by charged SCS, affecting kinetic-thermodynamic correlations.

Purpose of the Study:

• To systematically investigate the electrostatic contributions of positive charges in the SCS to electrocatalyst redox potentials.
• To understand how charged SCS impacts the observed linear free-energy scaling relationships.

Main Methods:

• A series of 11 iron carbonyl clusters were synthesized and modified with charged and uncharged ligands.
• Electrochemical measurements were performed to determine redox potentials.
• Infrared spectroscopy (IR) was used to probe changes in the νCO absorption band energy.

Main Results:

• A linear correlation between νCO absorption band energy and electrochemical redox potentials was observed for most catalysts.
• This linear correlation was disrupted in systems with positively charged SCS.
• The study quantifies the electrostatic influence of charged SCS on catalyst redox properties.

Conclusions:

• Positively charged SCS significantly influences electrocatalyst redox potentials, deviating from expected linear free-energy relationships.
• Understanding these electrostatic effects is crucial for accurate electrocatalyst design and benchmarking.
• Future electrocatalyst development should consider the impact of SCS charge on performance.