Enhanced Oxygen Storage Capacity of Porous CeO₂ by Rare Earth Doping

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Cerium oxide (CeO₂) is a crucial rare earth oxide widely used as an oxygen storage material.
• Its oxygen storage capacity (OSC) is vital for applications like catalytic converters.
• Enhancing OSC is a key objective for improving material performance.

Purpose of the Study:

• To enhance the oxygen storage capacity (OSC) of ceria (CeO₂) by doping with various rare earth (RE) ions.
• To synthesize and characterize undoped and RE-doped CeO₂ materials.
• To investigate the relationship between doping concentration, material properties, and OSC.

Main Methods:

• Solvothermal synthesis followed by calcination to produce undoped and RE-doped CeO₂.
• X-ray photoelectron spectroscopy (XPS) to analyze Ce 3d and O 1s core-levels for reducible Ceⁿ⁺ ions and oxygen vacancies.
• Raman spectroscopy for qualitative and quantitative analysis of oxygen vacancies.
• Hydrogen temperature-programmed reduction (H₂-TPR) to quantify OSC via H₂ consumption.
• Least-squares refinement using NaCl for lattice parameter determination.

Main Results:

• Undoped CeO₂ exhibited a unique porous multilayered morphology without templates.
• Solubility limits of RE ions in CeO₂ were determined.
• RE doping significantly increased the OSC of CeO₂, with maximum improvements observed at specific doping concentrations (e.g., 5 mol.% Yb, 4 mol.% Y, 4 mol.% Sm, 7 mol.% La).
• Specific OSC enhancements reached up to 93.04% (Yb-doped).

Conclusions:

• Rare earth doping is an effective strategy to enhance the oxygen storage capacity of ceria.
• The study identified optimal doping levels for different rare earth ions to maximize OSC.
• The findings provide insights into defect chemistry and its influence on the performance of doped ceria materials.