Size-Dependence of the Adsorption Energy of CO on Pt Nanoparticles: Tracing Two Intersecting Trends by DFT Calculations

Identification of active sites in heterogeneous metal catalysts is critical for understanding the reaction mechanism at the molecular level and for designing more efficient catalysts. Because of their structural flexibility, subnanometric metal catalysts, including single atoms and clusters with a few atoms, can exhibit dynamic structural evolution when interacting with substrate molecules, making it difficult to determine the catalytically active sites. In this work, Pt catalysts containing selected types of Pt entities (from single atoms to clusters and nanoparticles) have been prepared, and their evolution has been followed, while they were reacting in a variety of heterogeneous catalytic reactions, including selective hydrogenation reactions, CO oxidation, dehydrogenation of propane, and photocatalytic H2 evolution reaction. By in situ X-ray absorption spectroscopy, in situ IR spectroscopy, and high-resolution electron microscopy techniques, we will show that some characterization techniques carried out in an inadequate way can introduce confusion on the interpretation of coordination environment of highly dispersed Pt species. Finally, the combination of catalytic reactivity and in situ characterization techniques shows that, depending on the catalyst–reactant interaction and metal–support interaction, singly dispersed metal atoms can rapidly evolve into metal clusters or nanoparticles, being the working active sites for those abovementioned heterogeneous reactions.

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“…Nevertheless, the adsorption of CO behavior on Pt species could also be related to the particle size. 71…”

Section: Resultsmentioning

confidence: 99%

Determination of the Evolution of Heterogeneous Single Metal Atoms and Nanoclusters under Reaction Conditions: Which Are the Working Catalytic Sites?

et al. 2019

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“…polycrystalline electrodes. This is particularly evident considering adsorption energies [53], which have a deep impact on oxide growth and stripping, in the absence and presence of specifically adsorbing ions.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of oxide growth on Pt nanoparticles electrodes in the presence of competing halides by operando energy dispersive X-Ray absorption spectroscopy

Minguzzi

Montagna

Falqui

et al. 2018

Electrochimica Acta

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In this work we studied the kinetics of oxide formation and reduction on Pt nanoparticles in HClO 4 in the absence and in the presence of Brand Clions. The study combines potential step methods (i.e. chronoamperometry and choronocoulometry) with energy dispersive X-ray absorption spectroscopy (ED-XAS), which in principle allows to record a complete XAS spectrum in the timescale of milliseconds. Here, the information on the charge state and on the atomic surrounding of the considered element provided by XAS was exploited to monitor the degree of occupancy of 5d states of Pt in the course of oxide formation and growth, and to elucidate the competing halide adsorption/desorption phenomena. Electrochemical methods and XAS agree on the validity of a log(t) depending growth of Pt oxide, that is significantly delayed in the presence of Cland Branions. In the proximity of formation of one monolayer, the growth is further slowed down.

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“…On the other hand, such 1–2 nm large model NPs comprising few hundred atoms are already beyond the size range, where the quantum effects play role determining strong variation of properties [ 18 ]. Respectively, these model NPs belong to the scalable size range [ 18 , 35 , 38 ], which allows to extrapolate their properties to properties of NPs with 10 3 –10 4 atoms corresponding to operational experimental model catalysts (3–7 nm) [ 13 ]. Thus, the DFT parameterization of the TOP method [ 20 ] obtained for the 201-atomic NPs Pd x Au 201−x is applied to study the distribution of Pd and Au atoms in the isomorphic 586- and 1289-atomic models Pd x Au 586−x and Pd x Au 1289−x .…”

Section: Computational Details and Modeling Approachmentioning

confidence: 99%

Pd Single-Atom Sites on the Surface of PdAu Nanoparticles: A DFT-Based Topological Search for Suitable Compositions

et al. 2021

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Structure of model bimetallic PdAu nanoparticles is analyzed aiming to find Pd:Au ratios optimal for existence of Pd1 single-atom surface sites inside outer Au atomic shell. The analysis is performed using density-functional theory (DFT) calculations and topological approach based on DFT-parameterized topological energy expression. The number of the surface Pd1 sites in the absence of adsorbates is calculated as a function of Pd concentration inside the particles. At low Pd contents none of the Pd atoms emerge on the surface in the lowest-energy chemical orderings. However, surface Pd1 sites become stable, when Pd content inside a Pd-Au particle reaches ca. 60%. Further Pd content increase up to almost pure Pd core is accompanied by increased concentration of surface Pd atoms, mostly as Pd1 sites, although larger Pd ensembles as dimers and linear trimers are formed as well. Analysis of the chemical orderings inside PdAu nanoparticles at different Pd contents revealed that enrichment of the subsurface shell by Pd with predominant occupation of its edge positions precedes emergence of Pd surface species.

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Size-Dependence of the Adsorption Energy of CO on Pt Nanoparticles: Tracing Two Intersecting Trends by DFT Calculations

Cited by 43 publications

References 51 publications

Determination of the Evolution of Heterogeneous Single Metal Atoms and Nanoclusters under Reaction Conditions: Which Are the Working Catalytic Sites?

Determination of the Evolution of Heterogeneous Single Metal Atoms and Nanoclusters under Reaction Conditions: Which Are the Working Catalytic Sites?

Dynamics of oxide growth on Pt nanoparticles electrodes in the presence of competing halides by operando energy dispersive X-Ray absorption spectroscopy

Pd Single-Atom Sites on the Surface of PdAu Nanoparticles: A DFT-Based Topological Search for Suitable Compositions

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