Imaging Interface and Particle Size Effects by In Situ Correlative Microscopy of a Catalytic Reaction

Area of Science:

• Surface Science
• Catalysis
• Materials Science

Background:

• Understanding heterogeneous catalysis is crucial for chemical processes.
• Rhodium (Rh) catalysts are vital for many industrial applications.
• In situ characterization methods are needed to study dynamic catalytic processes.

Purpose of the Study:

• To investigate the in situ catalytic behavior of Rh nanoparticles on different supports (Rh, Au, ZrO2) during H2 oxidation.
• To correlate local structure and composition with catalytic performance.
• To elucidate the mechanisms behind kinetic transitions and self-sustaining oscillations.

Main Methods:

• Correlative photoemission electron microscopy (PEEM) and scanning photoemission electron microscopy (SPEM) for in situ observation.
• Micro-kinetic simulations based on hydrogen adsorption and oxygen binding.
• Analysis of Rh particle size and support material effects.

Main Results:

• Observed kinetic transitions between inactive and active steady states.
• Detected self-sustaining oscillations in catalytic activity, varying with support and Rh particle size.
• Identified surface alloy formation (Rh/Au) and substoichiometric Zr oxides (Rh/ZrO2) as key factors influencing oscillations.
• Rh/Au showed inhibited oscillations, Rh/ZrO2 showed size-dependent oscillations, and Rh/Rh showed size-independent oscillations.

Conclusions:

• Correlative in situ surface microscopy effectively links local structure, composition, and catalytic performance.
• Support material and particle size significantly influence Rh catalyst behavior in H2 oxidation.
• Mechanisms involve surface alloy formation and oxide layer dynamics on the support.