CO oxidation by Pt2/Fe3O4: metastable dimer and support configurations facilitate lattice oxygen extraction

TL;DR

This study reveals how metastable configurations of Pt dimers and Fe3O4 support facilitate lattice oxygen extraction, advancing understanding of CO oxidation mechanisms on single-atom catalysts.

Contribution

It combines experimental and computational methods to identify the active Pt2 dimers and their role in CO oxidation on Fe3O4, highlighting the importance of metastable states.

Findings

Pt2 dimers catalyze CO oxidation by extracting lattice oxygen.

Metastable configurations of both Pt dimers and support are crucial for reactivity.

Dynamic formation and dissociation of dimers influence catalytic activity.

Abstract

Heterogeneous catalysts based on sub-nanometer metal clusters often exhibit strongly size-dependent properties, and the addition or removal of a single atom can make all the difference. Identifying the most active species and deciphering the reaction mechanism is extremely difficult, however, because it is often not clear how the catalyst evolves in operando. Here, we utilize a combination of atomically resolved scanning probe microscopies, spectroscopic techniques, and density functional theory (DFT)-based calculations to study CO oxidation by a model Pt/Fe3O4(001) single-atom catalyst. We demonstrate that (PtCO)2 dimers, formed dynamically through the agglomeration of mobile Pt-carbonyl species, catalyse a reaction involving the oxide support to form CO2. Pt2 dimers produce one CO2 molecule before falling apart into two adatoms, releasing the second CO. Interestingly, Olattice extraction only becomes facile when both the Pt-dimer and the Fe3O4 support can access metastable configurations, suggesting that substantial, concerted rearrangements of both cluster and support must be considered for reactions occurring at elevated temperature.