Evidence for the Active Phase of Heterogeneous Catalysts through In Situ Reaction Product Imaging and Multiscale Modeling

TL;DR

This study combines multi-scale modeling and in situ reaction product imaging to identify the active phase of Pd(100) catalysts during CO oxidation, revealing that pristine Pd(100) predominantly drives catalytic activity under near-ambient conditions.

Contribution

The paper introduces an integrated approach using density-functional theory, kinetic Monte Carlo, and fluid dynamics to directly link surface models with experimental reaction signals.

Findings

Pristine Pd(100) is the main active phase during CO oxidation.

Coexistence of oxidic domains may influence activity.

Modeling accurately reproduces LIF measurements.

Abstract

We use multi-scale modeling to analyze laser-induced fluorescence (LIF) measurements of the CO oxidation reaction over Pd(100) at near-ambient reaction conditions. Integrating density-functional theory based kinetic Monte Carlo simulations of the active catalyst into fluid-dynamical simulations of the mass transport inside the reactor chamber we calculate the reaction product concentration directly above the catalyst surface. Comparing corresponding data calculated for different surface models against the measured LIF signals we can discriminate the one that predominantly actuates the experimentally measured catalytic activity. For the probed CO oxidation reaction conditions the experimental activity is due to pristine Pd(100), possibly coexisting with other (oxidic) domains on the surface.