Interrogating site dependent kinetics over SiO₂-supported Pt nanoparticles.

Area of Science:

• Catalysis
• Chemical Kinetics
• Materials Science

Background:

• Heterogeneous catalysis is vital for efficient chemical processes.
• Understanding site-specific reaction kinetics is challenging.
• Current methods face limitations due to pressure, material, and temperature gaps.

Purpose of the Study:

• To resolve and quantify distinct kinetic pathways for CO oxidation.
• To investigate CO oxidation over SiO2-supported 2 nm Pt nanoparticles.
• To bridge the complexity gap in heterogeneous catalysis.

Main Methods:

• Transient pressure pulse experiments were employed.
• In situ DRIFTS (in situ diffuse reflectance infrared Fourier transform spectroscopy) was used to characterize CO adsorption sites.
• Kinetic site deconvolution was performed.

Main Results:

• Two distinct pathways for CO oxidation were identified and quantified.
• Pathway distribution correlated with the distribution of well-coordinated and under-coordinated CO adsorption sites.
• Well-coordinated sites followed Langmuir-Hinshelwood kinetics, while under-coordinated sites exhibited non-standard, barrierless yet slow kinetics.

Conclusions:

• Site-dependent kinetics were successfully resolved, bypassing traditional experimental gaps.
• Under-coordinated sites on Pt nanoparticles show unique CO oxidation behavior.
• The kinetic site deconvolution method is broadly applicable to diverse catalytic systems.