An Atomic-Scale View of CO and H2 Oxidation on a Pt-Fe3O4 Model Catalyst

TL;DR

This study uses scanning tunneling microscopy to reveal atomic-scale mechanisms of CO and H2 oxidation on a Pt-Fe3O4 catalyst, highlighting metal-support interactions and reaction pathways at 550 K.

Contribution

It provides the first atomic-scale insights into how Pt catalysts interact with Fe3O4 supports during oxidation reactions, elucidating mechanisms of oxygen extraction and spillover effects.

Findings

CO extracts lattice oxygen forming CO2 and holes in the surface.

H2 and O2 dissociate on Pt clusters and spill over onto the support.

Pt catalyzes reactions that occur on bare Fe3O4 but at higher temperatures.

Abstract

Metal-support interactions are frequently invoked to explain the enhanced catalytic activity of metal nanoparticles dispersed over reducible metal-oxide supports, yet the atomic scale mechanisms are rarely known. Here, we use scanning tunneling microscopy to study a Pt1-6/Fe3O4 model catalyst exposed to CO, H2, O2, and mixtures thereof, at 550 K. CO extracts lattice oxygen at the cluster perimeter to form CO2, creating large holes in the metal-oxide surface. H2 and O2 dissociate on the metal clusters and spill over onto the support. The former creates create surface hydroxyl groups, which react with the support to desorb water, while atomic oxygen reacts with Fe from the bulk to create new Fe3O4(001) islands. The presence of the Pt is crucial because it catalyses reactions that already occur on the bare iron-oxide surface, but at higher temperatures.