Fast Outer-Sphere Electron Transfer and High Specific Capacitance at Covalently Modified Carbon Electrodes.

Area of Science:

• Electrochemistry
• Materials Science
• Surface Chemistry

Background:

• Carbon electrodes often suffer from slow electron transfer due to surface contamination.
• Adventitious molecules adsorb onto graphitic carbon surfaces, hindering electrochemical reactions.

Purpose of the Study:

• To develop a method for permanently modifying graphitic carbon electrodes to be hydrophilic.
• To investigate the electrochemical properties of these modified electrodes.

Main Methods:

• Functionalization of graphitic carbon electrodes with 4-(diazonium)benzenesulfonic acid.
• Electrochemical characterization using cyclic voltammetry in aqueous electrolytes.
• Evaluation of electron transfer kinetics with redox couples and in redox flow batteries.

Main Results:

• The modified electrodes became permanently hydrophilic.
• Achieved metal-like specific capacitance (approximately 40 μF/cm²) indicating altered double-layer structure.
• Demonstrated fast charge transfer kinetics for outer-sphere redox couples.
• Showed improved electron transfer kinetics in alkaline aqueous redox flow batteries.

Conclusions:

• Surface functionalization with 4-(diazonium)benzenesulfonic acid effectively renders graphitic carbon electrodes hydrophilic.
• The hydrophilic modification significantly enhances electrochemical performance, including capacitance and electron transfer rates.
• These improved properties make the modified carbon electrodes promising for advanced electrochemical energy storage and conversion systems.