In Situ Formation of Ba₃CoNb₂O₉/Ba₅Nb₄O₁₅ Heterostructure in Electrolytes for Enhancing Proton Conductivity and SOFC...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Conversion

Background:

• Solid oxide fuel cells (SOFCs) require advanced electrolytes for improved efficiency.
• In situ heterostructure formation offers superior electrochemical properties compared to mechanical mixing.
• Developing novel electrolytes is crucial for next-generation energy devices.

Purpose of the Study:

• To design and investigate an in situ formed Ba3CoNb2O9/Ba5Nb4O15 heterostructure as an electrolyte for SOFCs.
• To understand the impact of Co-ion diffusion on heterostructure formation and electrochemical performance.
• To analyze the abnormal temperature-dependent performance of the SOFC.

Main Methods:

• Fabrication of an SOFC using a Ba5Nb4O15 electrolyte and a Ni0.8Co0.15Al0.05LiO2-δ anode.
• In situ formation of the Ba3CoNb2O9/Ba5Nb4O15 heterostructure via Co-ion diffusion during cell operation.
• Characterization using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).
• Electrochemical performance testing, including power density measurements at various temperatures.

Main Results:

• The in situ Ba3CoNb2O9/Ba5Nb4O15 heterostructure was successfully formed.
• An anomalous peak power density of 703 mW/cm2 was achieved at 510 °C, higher than at 550 °C.
• Operating temperature influenced Co doping concentration, affecting heterostructure conductivity.
• The heterojunction effectively restricted electron migration and enhanced proton conductivity.

Conclusions:

• The in situ formed Ba3CoNb2O9/Ba5Nb4O15 heterostructure demonstrates significant potential as an SOFC electrolyte.
• The unique temperature-dependent performance highlights the complex interplay between doping, structure, and conductivity.
• This study provides valuable insights into designing advanced electrolytes for efficient solid oxide fuel cells.