Tuning La₂O₃ to high ionic conductivity by Ni-doping

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lanthanum oxide (La₂O₃) is a wide-band gap semiconductor with potential for ionic conduction.
• Developing efficient ionic conducting materials is crucial for advancing fuel cell technology.

Purpose of the Study:

• To develop and characterize Ni-doped La₂O₃ as an ionic conducting membrane.
• To investigate the mechanisms behind performance enhancement in Ni-doped La₂O₃.
• To evaluate its potential for fuel cell applications.

Main Methods:

• Synthesis of Ni-doped La₂O₃ membranes.
• Electrochemical impedance spectroscopy to measure ionic conductivity.
• X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy for material characterization.
• Density functional theory (DFT) calculations to understand electronic structure.
• Fuel cell testing to determine power density and open circuit voltage.

Main Results:

• Achieved ionic conductivity of 0.187 S cm^-1 at 550 °C with Ni-doped La₂O₃.
• Attained a peak power density of 970 mW cm^-2 and an open circuit voltage of 1.05 V.
• Identified high oxygen vacancy concentration as key to performance enhancement.
• DFT calculations confirmed Ni doping tunes the band structure for improved electrochemical performance.
• Formation of a Schottky junction barrier at the anode/electrolyte interface facilitated ionic transport.

Conclusions:

• Ni-doped La₂O₃ demonstrates excellent ionic conducting properties suitable for fuel cells.
• Oxygen vacancies and tailored electronic band structure are critical for enhanced performance.
• Wide-band gap semiconductors can be engineered for advanced ionic conductor applications through doping.