Tunable Oxygen Functional Groups as Electrocatalysts on Graphite Felt Surfaces for All-Vanadium Flow Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Graphite felt electrodes are crucial for all-vanadium redox flow batteries (VRB).
• Surface functionalization can enhance electrode performance in electrochemical systems.
• Optimizing oxygen functional groups is key to improving VRB efficiency.

Purpose of the Study:

• To develop a dual oxidative approach for functionalizing graphite felt electrodes.
• To investigate the impact of specific oxygen functional groups on VRB performance.
• To elucidate the mechanisms behind performance enhancement in VRB cells.

Main Methods:

• A dual oxidative treatment using O2 plasma followed by H2O2 was applied to graphite felt electrodes.
• Electrochemical performance of the functionalized electrodes was evaluated in an all-vanadium redox flow battery system.
• Surface functional groups were analyzed to correlate their type and amount with cell performance.

Main Results:

• The dual oxidative treatment significantly enhanced VRB cell energy efficiency by 8.2% at 150 mA cm⁻² compared to thermal oxidation.
• Specific oxygen functional groups, particularly O-C=O, were found to improve cell performance.
• Other groups like C-O and C=O were identified as detrimental to VRB performance.
• A reduction in cell overpotential was observed after graphite felt functionalization.

Conclusions:

• The dual oxidative approach is an effective method for enhancing graphite felt electrodes for VRB applications.
• Tailoring oxygen functional groups, especially promoting O-C=O, can significantly improve VRB energy efficiency and reduce overpotential.
• This research offers a cost-effective route for developing more commercially viable stationary energy storage solutions using VRB technology.