Oxygen-Vacancy-Engineered Tm-Doped CeO₂ Electrolyte for Efficient Low-Temperature Solid Oxide Fuel Cells

Area of Science:

• Materials Science
• Electrochemistry
• Solid Oxide Fuel Cells

Background:

• Developing efficient solid electrolytes for low-temperature solid oxide fuel cells (LT-SOFCs) is crucial.
• Thulium-doped ceria (TDC) is explored as a potential high-performance electrolyte material.

Purpose of the Study:

• To synthesize and characterize thulium-doped ceria (Ce _0.75Tm _0.25O _2-δ) for LT-SOFC applications.
• To evaluate the structural, microstructural, and electrochemical properties of TDC.
• To understand the electronic structure contributions to TDC's performance.

Main Methods:

• Solid-state reaction synthesis.
• X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray Photoelectron Spectroscopy (XPS) for characterization.
• Electrochemical testing and impedance spectroscopy.
• First-principles calculations for electronic structure analysis.

Main Results:

• TDC exhibits a stable cubic fluorite phase with homogeneous Tm incorporation and oxygen vacancies.
• Nanoscale grains and lattice expansion were observed, enhancing ion transport.
• The LT-SOFC with TDC achieved a peak power density of 897 mW cm^-2 at 550 °C with an open-circuit voltage of 1.10 V.
• High ionic conductivity (0.14 S cm^-1 at 550 °C) was confirmed, with low ohmic and polarization resistances.
• Electronic structure calculations revealed spin polarization and p-d hybridization contributing to performance.

Conclusions:

• Thulium-doped ceria is a high-performance electrolyte for LT-SOFCs.
• Defect engineering and electronic structure modulation are key to TDC's multifunctional behavior.
• TDC shows significant promise for next-generation LT-SOFCs and multifunctional energy devices.