Mechanistic study on the enhanced N₂ selectivity for NH₃ selective oxidation over Pt-encapsulated Cu-ZSM-5 catalysts

Area of Science:

• Catalysis
• Environmental Chemistry
• Materials Science

Background:

• Ammonia (NH3) is a promising zero-carbon fuel but its emissions cause air pollution (PM2.5) and disrupt the nitrogen cycle.
• Selective Catalytic Oxidation (SCO) is key for NH3 treatment, but achieving high activity and N2 selectivity over wide temperature ranges is difficult.

Purpose of the Study:

• To develop a highly efficient catalyst for ammonia abatement.
• To understand the synergistic effects in a dual-site catalyst for improved N2 selectivity.

Main Methods:

• Fabrication of a core-shell Pt@Cu-ZSM-5 catalyst with encapsulated Pt clusters within Cu-exchanged ZSM-5.
• Testing the catalyst's performance for NH3 conversion and N2 selectivity across a broad temperature range (250-500°C).
• Conducting mechanistic studies to elucidate the roles of Pt and Cu sites in the catalytic process.

Main Results:

• The optimal Pt@Cu-ZSM-5 catalyst achieved complete NH3 conversion below 250°C.
• Over 92% N2 selectivity was maintained from 250°C to 500°C.
• Mechanistic studies revealed synergistic effects between Pt and Cu sites, inhibiting N2O formation and reducing NOx emissions.

Conclusions:

• The Pt@Cu-ZSM-5 catalyst demonstrates superior performance for NH3 abatement, offering a viable solution for emissions control.
• The study provides insights into designing bifunctional catalysts by understanding Pt-Cu synergistic interactions.
• This work contributes to the development of cleaner energy technologies utilizing ammonia.