High Power Density and Stable Fuel Cells with 18-Phosphomolybdic Acid as Oxygen Reduction Reaction Mediator

Area of Science:

• Electrochemistry
• Materials Science
• Energy Conversion

Background:

• Mediated fuel cells (MedFCs) present an alternative to proton exchange membrane fuel cells.
• Current mediators face challenges with electrochemical activity and stability, limiting MedFC performance.
• Addressing these limitations is crucial for advancing fuel cell technology.

Purpose of the Study:

• To introduce a novel redox mediator for enhanced oxygen reduction reaction (ORR) activity and stability in MedFCs.
• To evaluate the performance and durability of MedFCs utilizing the new mediator.
• To demonstrate a viable alternative to precious metal catalysts and complex management systems.

Main Methods:

• Utilized a Dawson-type 18-molybdophosphoric heteropoly acid (18-PMA) as the redox mediator.
• Employed ordinary carbon felt electrodes in the mediated fuel cell setup.
• Assessed fuel cell performance through power density measurements and stable discharge tests.
• Investigated long-term stability via catalyst replacement in an external reactor.

Main Results:

• Achieved a maximum steady-state power density of 600 mW cm⁻² under dry conditions.
• Demonstrated stable discharge performance across a current density range of 100–500 mA cm⁻².
• Confirmed long-term stability through a straightforward Fe-N-C catalyst replacement method.

Conclusions:

• 18-PMA exhibits high redox activity and stability, making it an effective ORR mediator.
• MedFCs employing 18-PMA show significant performance and stability improvements.
• This approach offers a promising pathway for efficient and durable fuel cell applications.