Design Strategies for High-Performance NH₃-SCO Catalysts: Identifying and Modulating Direct Anchoring Sites for Ag on...

Area of Science:

• Catalysis
• Materials Science
• Environmental Science

Background:

• Ammonia (NH3) slip from diesel aftertreatment and NH3-fueled engines causes environmental issues.
• Silver (Ag)-based catalysts are crucial for NH3 selective catalytic oxidation (NH3-SCO) to N2.
• Identifying Ag anchoring sites on TiO2 supports is vital for catalyst performance but remains debated.

Purpose of the Study:

• To determine the direct anchoring sites of Ag on TiO2 for NH3-SCO.
• To investigate the relationship between Ag dispersion and TiO2 surface properties (hydroxyl groups and defects).
• To optimize catalyst performance by controlling Ag anchoring sites.

Main Methods:

• Density Functional Theory (DFT) calculations to identify Ag anchoring sites.
• Thermal treatment to modulate hydroxyl (OH) group content on TiO2.
• In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and kinetic studies.

Main Results:

• Surface OH groups on TiO2 were confirmed as direct anchoring sites for Ag.
• Optimizing OH group content (on TiO2-800) led to larger metallic Ag nanoparticles (Ag0 NPs).
• Enhanced Ag0 NPs facilitated O2 activation and NH3 dissociation, improving NH3-SCO efficiency.

Conclusions:

• Surface OH groups are critical for anchoring Ag, influencing catalyst performance in NH3-SCO.
• Modulating OH group content offers a strategy for designing efficient Ag-based NH3-SCO catalysts.
• The findings can guide the rational design of catalysts for other metal-support systems.