CO oxidation by Pt ₂ /Fe ₃ O ₄ : Metastable dimer and support configurations facilitate lattice oxygen extraction

Abstract

Heterogeneous catalysts based on subnanometer 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 use 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/Fe 3 O 4 (001) “single-atom” catalyst. We demonstrate that (PtCO) 2 dimers, formed dynamically through the agglomeration of mobile Pt-carbonyl species, catalyze a reaction involving the oxide support to form CO 2 . Pt 2 dimers produce one CO 2 molecule before falling apart into two adatoms, releasing the second CO. O lattice extraction only becomes facile when both the Pt-dimer and the Fe 3 O 4 support can access metastable configurations, suggesting that substantial, concerted rearrangements of both cluster and support must be considered for reactions occurring at elevated temperature.

Recent Progress of Diatomic Catalysts: General Design Fundamentals and Diversified Catalytic Applications

“…In the process of CO oxidation catalyzed by Pt/Fe 3 O 4 model catalyst, the dynamically formed Pt 2 dimer was conducive to the extraction of oxygen from the carrier lattice at 525 K (252 °C) to promote CO oxidation (see Figure ). [ 47 ] The initial state of the Pt/Fe 3 O 4 (001) monoatomic catalyst was characterized by scanning tunneling microscopy (STM) and noncontact atomic force microscopy (ncAFM) (see Figure 23a–c), which confirmed the geometry of (PtCO) 2 determined by DFT calculations and allowed direct imaging of individual CO molecules adsorbed on sub‐nanoclusters (see Figure 23d,e). The researchers found that CO oxidation occurs in a metastable (PtCO) 2 configuration, which is the key intermediate configuration of Pt/Fe 3 O 4 (001) catalyst during the catalytic reaction at high temperature.…”

“…[125] Further density functional theory calculations show that the electron redistribution and bandgap narrowing caused by the bonded FeN 4 and CuN 3 moieties enhance the electron conductivity and enhance the bonding interaction between the *COOH intermediate and the Fe center, thus reducing the overall reaction barrier and promoting the generation of CO. [126] The prepared Fe/CuNC diatomic catalyst has (a-e) Reproduced with permission. [47] Copyright 2022, Science.…”

“…In the process of CO oxidation catalyzed by Pt/Fe 3 O 4 model catalyst, the dynamically formed Pt 2 dimer was conducive to the extraction of oxygen from the carrier lattice at 525 K (252 °C) to promote CO oxidation (see Figure 23). [47] The initial state of the Pt/Fe 3 O 4 (001) monoatomic catalyst was characterized by scanning tunneling microscopy (STM) and noncontact atomic force microscopy (ncAFM) x-y line scan intensity profile of isolated sites as distance. (a-f) Reproduced with permission.…”

“…[7,19,20,36,[39][40][41][42] In addition, with respect to the category of DACs, more researches have been focused on carbonbased DACs, [36,[39][40][41][42] and other kinds of DACs (noncarbonbased DACs) have not been more clearly demarcated and outlined. [43][44][45][46][47][48] In terms of the applications of DACs, most of the existing studies have focused on the use of DACs in electrocatalysis, [7,19,20,40] and at present, the research on the application of thermocatalysis and photocatalysis is gradually app eared. [28,34,44,[48][49][50][51][52][53] At present, there is a lack of review article that can effectively combine the metal interaction principle, supporting effect, preparation method, optimization strategy, structural characterization, and multiple catalytic applications of DACs to reach a systematic design theory and wide readership appeal.…”

“…e) ncAFM simulations based on the structure shown in (d), with different CO surface separations. (a-e) Reproduced with permission [47]. Copyright 2022, Science.…”