Understanding water management in platinum group metal-free electrodes using neutron imaging

Area of Science:

• Electrochemistry
• Materials Science
• Energy Conversion

Background:

• Platinum group metal-free (PGM-free) catalysts offer a cost-effective alternative to PGM catalysts in polymer electrolyte fuel cells.
• Thicker electrodes are required for PGM-free catalysts due to lower volumetric activity, leading to transport and water management issues.
• Poor water management in PGM-free electrodes limits overall fuel cell performance.

Purpose of the Study:

• To investigate water management challenges in PGM-free electrodes.
• To understand transport limitations within thick PGM-free electrodes.
• To identify strategies for improving fuel cell performance by optimizing water removal.

Main Methods:

• In-operando neutron imaging was employed to quantify water content across fuel cell components.
• Comparative analysis of water saturation in PGM-free and PGM electrodes under various operating conditions.
• Evaluation of three distinct methods to enhance water removal from PGM-free electrodes.

Main Results:

• PGM-free electrodes exhibit higher water saturation than PGM electrodes, even with similar catalyst layer thicknesses, due to superior water retention.
• Neutron imaging revealed significant water accumulation in PGM-free electrodes.
• Implemented strategies demonstrated improvements in water removal and fuel cell performance.

Conclusions:

• High water retention by PGM-free catalysts is a key factor in electrode flooding.
• Optimizing water removal through novel microporous layers, anode gas diffusion layers, and increased catalyst porosity can significantly improve fuel cell performance.
• Addressing water management is crucial for realizing the potential of PGM-free catalysts in fuel cells.