A Stable and Efficient Cathode for Fluorine-Containing Proton-Conducting Solid Oxide Fuel Cells.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Conversion

Background:

• Proton-conducting electrolytes are crucial for solid oxide fuel cells (SOFCs).
• Anion substitution (e.g., F⁻, Cl⁻) can enhance electrolyte stability but may lead to cathode migration issues.
• Developing stable and efficient cathode materials is essential for SOFC longevity.

Purpose of the Study:

• To investigate the effect of fluorine (F⁻) doping in Ba$_{0.5}$ Sr$_{0.5}$ Co$_{0.8}$ Fe$_{0.2}$ O$_{3-δ}$ (BSCF) as a cathode material for proton-conducting SOFCs.
• To improve the stability of SOFCs by mitigating F⁻ diffusion from the electrolyte to the cathode.
• To enhance the electrochemical performance of the cathode.

Main Methods:

• Synthesis of F⁻-doped BSCF (F-BSCF) cathode material.
• Fabrication and testing of button cells using F-BSCF cathodes and BaCe$_{0.8}$ Sm$_{0.2}$ F$_{0.1}$ O$_{2.85}$ electrolyte.
• Analysis using temperature-dependent X-ray photoelectron spectroscopy (XPS) and electronic conductivity relaxation (ECR).

Main Results:

• F⁻ incorporation into BSCF effectively suppressed F⁻ diffusion from the electrolyte, significantly improving button cell stability.
• Temperature-dependent XPS and ECR confirmed enhanced oxygen incorporation kinetics at intermediate temperatures.
• The F-BSCF cathode demonstrated improved catalytic activity and superior long-term stability (270 h at 300 mA cm⁻² and 700°C) compared to undoped BSCF.

Conclusions:

• Fluorine doping of BSCF is a viable strategy to create stable and high-performance cathodes for proton-conducting SOFCs.
• The F-BSCF cathode mitigates critical issues related to ion migration, leading to enhanced operational durability.
• This work presents a promising cathode material for advancing proton-conducting SOFC technology.