La4LiAuO8 and La2BaPdO5: comparing two highly stable d8 square-planar oxides

Area of Science:

• Materials Science
• Heterogeneous Catalysis
• Inorganic Chemistry

Background:

• Isolated and immobilized metal ions are crucial in heterogeneous catalysis.
• Understanding the role of Au(3+) and Pd(2+) in oxide environments is key for catalyst design.

Purpose of the Study:

• To characterize La(4)LiAuO(8) and La(2)BaPdO(5) as model compounds for studying isolated Au(3+) and Pd(2+) in catalysis.
• To evaluate their structural, stability, surface, and electronic properties.
• To assess their efficacy as heterogeneous catalysts for CO oxidation.

Main Methods:

• Synchrotron X-ray scattering (pair distribution function and maximum entropy method analysis).
• Density functional theory calculations for electronic structures.
• Thermogravimetric analysis for stability verification.

Main Results:

• Exceptional stability of the oxides attributed to covalent Au-O and Pd-O interactions.
• La(2)BaPdO(5) demonstrated effective CO oxidation catalysis, a first for ordered Pd(2+) oxides.
• La(4)LiAuO(8) showed significantly lower catalytic activity.

Conclusions:

• Covalent metal-oxygen interactions are crucial for stabilizing oxophobic metals in oxides.
• Ordered Pd(2+) oxides can be effective heterogeneous catalysts for CO oxidation.
• Electronic structure differences correlate with catalytic performance variations.