Metal Precursor Composition Is Key in the Synthesis of Pd Single Atom Catalysts.

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Single-atom catalysts (SACs) offer superior metal utilization and unique catalytic properties.
• Achieving uniform atomic dispersion of platinum-group metals (PGMs) is difficult due to aggregation, even at low loadings.
• Reliable SAC development needs guiding principles for atomic dispersion.

Purpose of the Study:

• To investigate how metal precursor characteristics influence the structure of deposited palladium (Pd) domains on γ-Al₂O₃.
• To establish principles for promoting atomic dispersion in scalable catalyst synthesis.
• To compare the effects of different Pd precursors on dispersion.

Main Methods:

• Scalable impregnation synthesis of Pd on γ-Al₂O₃.
• Varying metal precursor characteristics, specifically the nature of counterions and coordinating ligands.
• Characterization of deposited Pd domain structures.

Main Results:

• Palladium-nitrate precursors form polynuclear hydroxo complexes, leading to Pd cluster formation.
• Palladium-ammonia precursors, like tetraammine Pd nitrate, stabilize Pd via NH₃ ligands, inhibiting aggregation.
• Improved atomic dispersion of Pd on γ-Al₂O₃ was achieved using Pd-ammonia precursors.

Conclusions:

• Metal precursor choice significantly impacts PGM atomic dispersion on supports.
• Optimizing precursor ligands (e.g., ammonia) is crucial for preventing aggregation.
• This work provides a pathway for reproducible synthesis of highly dispersed SACs.