Tunnel-Structured Phosphate Exhibiting High Proton Conductivity and Thermal Stability over a Wide Intermediate...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Developing stable proton solid electrolytes for fuel cells operating at intermediate temperatures is crucial for practical vehicle applications.
• Existing materials often struggle to balance thermal stability with high proton conductivity across a wide temperature range.

Purpose of the Study:

• To investigate the proton conductivity and thermal stability of a novel tunnel structured phosphate, KNi_1-H₂(PO₃)₃·yH₂O.
• To evaluate its potential as a proton solid electrolyte for next-generation fuel cells.

Main Methods:

• Synthesis and characterization of tunnel structured phosphate KNi_1-H₂(PO₃)₃·yH₂O.
• Proton conductivity measurements from room temperature up to 500 °C.
• Thermal stability analysis up to 600 °C.
• Atmospheric stability tests under various gas flows (N₂, H₂/Ar, O₂).

Main Results:

• The material exhibits high proton conductivity (1.7 × 10^-2 S cm^-1 at 275 °C) and maintains a rigid framework up to 600 °C.
• Proton conduction occurs via water molecules within the tunnel structure.
• Stable conductivity (5.0 × 10^-3 S cm^-1 at 150 °C) was observed for 10 hours under different atmospheric conditions.

Conclusions:

• Tunnel structured phosphate KNi_1-H₂(PO₃)₃·yH₂O shows significant potential as a proton solid electrolyte.
• Its properties are suitable for applications in advanced fuel cells requiring thermal stability and high proton conductivity.