A proton conductor electrolyte based on molten CsH₅(PO₄)₂ for intermediate-temperature fuel cells

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Molten carbonate fuel cells (MCFCs) are a mature technology, benefiting from liquid electrolytes for gas sealing and low contact resistance.
• MCFCs operate at high temperatures (500-700 °C), necessitating ceramic support matrices for their electrolytes.

Purpose of the Study:

• To investigate the potential of a novel molten oxoacid salt as a fuel cell electrolyte.
• To evaluate the performance and properties of a molten proton conductor electrolyte operating at reduced temperatures.

Main Methods:

• A novel electrolyte membrane was fabricated using molten CsH5(PO4)2 immobilized within a PBI polymer and SiO2 powder matrix.
• A molten proton conductor fuel cell was assembled using this membrane and tested at 200 °C.

Main Results:

• The developed electrolyte membrane exhibited excellent thermal stability, good mechanical properties, and high proton conductivity.
• The fuel cell demonstrated a high open-circuit voltage of 1.08 V.
• Stable output voltage was maintained for 150 hours at a current density of 100 mA cm⁻².

Conclusions:

• Molten oxoacid salts offer a viable alternative electrolyte for fuel cells, enabling operation at lower temperatures (150-250 °C) compared to MCFCs.
• The PBI/SiO2-supported CsH5(PO4)2 electrolyte membrane shows significant potential for efficient and durable fuel cell applications.