Pd2+/Pd0 redox cycling in hexagonal YMn(0.5)Fe(0.5)O3: implications for catalysis by PGM-substituted complex oxides

Area of Science:

• Solid-state chemistry
• Materials science
• Catalysis

Background:

• Complex oxides can exhibit redox cycling of platinum group metals (PGMs) like palladium (Pd).
• Pd-substituted complex oxides can reversibly extrude metallic Pd and reincorporate Pd(2+) ions.

Purpose of the Study:

• To synthesize and characterize YMn(0.5)Fe(0.5-x)Pd(x)O(3-δ) complex oxides.
• To investigate the redox cycling behavior of Pd within these complex oxides.
• To evaluate the catalytic performance for CO oxidation.

Main Methods:

• Sol-gel synthesis at 800 °C.
• High-resolution synchrotron X-ray powder diffraction for structural refinement.
• Synchrotron X-ray diffraction and EXAFS studies for redox cycling monitoring.
• Testing catalytic activity for CO oxidation.

Main Results:

• YMn(0.5)Fe(0.5-x)Pd(x)O(3-δ) compounds were successfully synthesized and characterized.
• The materials showed modest tolerance to redox cycling, forming stable PdO.
• Catalytic performance for CO oxidation was comparable to previously studied materials and finely dispersed PdO.
• No significant catalytic improvement was observed with increasing Pd substitution.

Conclusions:

• The hexagonal YMnO(3) structure does not efficiently facilitate oxygen transport for improved catalysis.
• Solid-state chemistry and structural factors influence PGM redox cycling efficacy and catalytic performance in complex oxides.
• Limited redox cycling tolerance and lack of enhanced catalytic activity were observed in these specific Pd-substituted complex oxides.