Toward a Comprehensive Understanding of Cation Effects in Proton Exchange Membrane Fuel Cells

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Metal alloy catalysts, such as platinum-cobalt (Pt-Co), enhance oxygen reduction reaction kinetics in fuel cells.
• Alloying element leaching leads to ionomer/membrane contamination, compromising fuel cell durability.
• Mechanisms of cation contamination effects on fuel cell performance are not fully understood.

Purpose of the Study:

• To provide a comprehensive understanding of cation contamination effects in fuel cell electrodes.
• To identify the specific mechanisms and locations of performance loss due to cation contamination.
• To inform strategies for mitigating negative impacts of alloy leaching in fuel cells.

Main Methods:

• Controlled doping of electrodes with cations.
• Electrochemical testing coupled with membrane conductivity and water uptake measurements.
• Impedance modeling to pinpoint performance loss origins.

Main Results:

• Up to approximately 44% cobalt (Co2+) exchange in the ionomer can be tolerated within the electrode.
• Performance loss is primarily attributed to oxygen (O2) and proton transport limitations.
• Cobalt (Co2+) cations preferentially accumulate in the electrode under humid operating conditions.

Conclusions:

• This study offers a mechanistic explanation for cation contamination effects in fuel cells.
• Findings guide the development of strategies to improve the durability of alloy catalysts.
• Understanding cation behavior is crucial for advancing fuel cell technology.