Finite-Size Effects in O and CO Adsorption for the Late Transition Metals

Peterson, Andrew A.; Grabow, Lars C.; Brennan, Thomas P.; Shong, Bonggeun; Ooi, Chin Chun; Wu, Di; Li, Christina; Kushwaha, Amit; Medford, Andrew J.; Mbuga, Felix; Li, Lin; Nørskov, Jens K.

doi:10.1007/s11244-012-9908-x

Cited by 71 publications

(98 citation statements)

References 45 publications

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“…The earlier reaction onset in the case of the wider Pt belt (Pt 2+ ) is likely related to weaker bound Pt-CO at the Ru-Pt interface. For a two (or more) Pt atom wide belt, Pt atoms at the interface have an average coordination number of 9 and are expected to be less reactive than Pt atoms directly at the edge, which have a coordination number of 7 [61]. This interpretation is consistent with the observation of the Pt oxidation/reduction cycle for RuPt ML-CE /Au(111) (Pt 2+ ), which indicates the preservation of Pt-like behavior.…”

Section: Discussionsupporting

confidence: 77%

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

et al. 2015

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A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface.

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Section: Discussionsupporting

confidence: 77%

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

et al. 2015

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“…This is not unexpected, as surface compression is well-known to occur at solid−gas interfaces. The magnitude of the observed bond compression, however, suggests that the relationship between CN and adsorbate binding energy calculated using surfaces or fixed bulk geometries 6,9,10 may be significantly different than for fully relaxed small supported clusters, in particular, on amorphous supports. On the basis of our results, we expect the effects of metal−support interactions on adsorbate binding energies to be complicated because NP− support interactions give rise to two competing phenomena, namely, an increase in bond compression, which generally weakens adsorbate binding, and a decrease in CN, which generally enhances adsorbate binding.…”

Section: ■ Introductionmentioning

confidence: 88%

“…This information cannot be obtained from experiments alone, 14 and current modeling approaches almost always ignore the amorphous nature of the support. 6,[9][10][11]15,16 Generating atomistic models of supported NPs on amorphous supports poses challenges not faced when using crystalline surfaces, because of the diversity of surface features and atomic surface roughness. The present work focuses on the development of a transferable methodology for studying the relaxation of catalytic nanoparticles on amorphous supports; we apply this methodology to investigate catalyst− support interactions between Pt and amorphous silica.…”

Section: ■ Introductionmentioning

confidence: 99%

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Structural and Electronic Properties of Pt₁₃ Nanoclusters on Amorphous Silica Supports

et al. 2015

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An accurate description of metal nanoparticle (NP)−support interactions is required for designing and optimizing NP catalytic systems because NP−support interactions may significantly impact NP stability and properties, such as catalytic activity. The ability to calculate NP interactions with amorphous supports, which are commonly used in industrial practice, is hampered because of a general lack of accurate atomically detailed model structures of amorphous surfaces. We have systematically studied relaxation processes of Pt 13 NPs on amorphous silica using recently developed realistic model amorphous silica surfaces. We have modeled the NP relaxation process in multiple steps: hard-sphere interactions were first used to generate initial placement of NPs on amorphous surfaces, then Pt−silica bonds were allowed to form, and finally both the NP and substrate were relaxed with density functional theory calculations. We find that the amorphous silica surface significantly impacts the morphology and electronic structure of the Pt clusters. Both NP energetics and charge transfer from NP to the support depend linearly on the number of Pt−silica bonds. Moreover, we find that the number of Pt−silica bonds is determined by the silica silanol number, which is a function of the silica pretreatment temperature. We predict that catalyst stability and electronic charge can be tuned via the pretreatment temperature of the support materials. The extent of support effects suggests that experiments aiming to measure the intrinsic catalytic properties of very small NPs on amorphous supports will fail because the measurable catalytic properties will depend critically on metal−support interactions. The magnitude of support effects highlights the need for explicitly including amorphous supports in atomistic studies.

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“…Coordination numbers below twelve are typical of surfaces and correspond to atoms with tendencies towards the formation of bonds that compensate for the lack of coordination. Hence, there is a proportionality relationship between the lack of coordination of surface atoms and their response towards the formation of new bonds, [7] following bond-order conservation theory.…”

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Fast Prediction of Adsorption Properties for Platinum Nanocatalysts with Generalized Coordination Numbers

Calle‐Vallejo

Martínez²,

Garcı́a-Lastra³

et al. 2014

Angewandte Chemie

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Platinum is a prominent catalyst for a multiplicity of reactions because of its high activity and stability. As Pt nanoparticles are normally used to maximize catalyst utilization and to minimize catalyst loading, it is important to rationalize and predict catalytic activity trends in nanoparticles in simple terms, while being able to compare these trends with those of extended surfaces. The trends in the adsorption energies of small oxygen-and hydrogen-containing adsorbates on Pt nanoparticles of various sizes and on extended surfaces were analyzed through DFT calculations by making use of the generalized coordination numbers of the surface sites. This simple and predictive descriptor links the geometric arrangement of a surface to its adsorption properties. It generates linear adsorption-energy trends, captures finite-size effects, and provides more accurate descriptions than d-band centers and usual coordination numbers. Unlike electronic-structure descriptors, which require knowledge of the densities of states, it is calculated manually. Finally, it was shown that an approximate equivalence exists between generalized coordination numbers and d-band centers.The increasing global demand for energy, the current dependence on fossil fuels, and the need for carbon-neutral processes call for the use of renewable energy sources and their associated technologies.[1] Among these, catalysis-based technologies, such as fuel cells and electrolyzers, promise to generate, store, and transform clean energy by means of the cleavage and formation of chemical bonds. However, high costs and efficiency and durability problems hinder the widespread implementation of these technologies.[2] The costs are lowered by using nanoparticles, as their high surface area to volume ratio reduces catalyst loadings. The challenge is to find appropriate catalyst sizes and morphologies for given catalytic purposes. Experimentally, this requires facile synthesis methods that permit the preferential formation of active sites with the highest turnover frequencies.[3] From a theoretical standpoint, simple and robust models are required with sound physical-chemical foundations and predictive power, that is, they must be able to univocally locate new information within existing trends. The most successful example of such models is arguably that of Hammer and Nørskov.[4] Their d-band model provides explanations of the reactivity of late transition metals based on a single parameter: the d-band center of the surface atoms. Nevertheless, it requires the computational calculation of projected densities of states (pDOS) on the surface atoms and has some limitations, such as a loss of accuracy for early transition metals, metals with fully filled d-bands, and strongly correlated metals. [5] Moreover, theoretical chemistry nowadays encounters the need for more realistic descriptions of catalytic nanoparticles. Instead of using model approaches such as Wulff constructions to describe complex nanostructures, first-principles simulations of entire nan...

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Finite-Size Effects in O and CO Adsorption for the Late Transition Metals

Cited by 71 publications

References 45 publications

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

Structural and Electronic Properties of Pt₁₃ Nanoclusters on Amorphous Silica Supports

Fast Prediction of Adsorption Properties for Platinum Nanocatalysts with Generalized Coordination Numbers

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Finite-Size Effects in O and CO Adsorption for the Late Transition Metals

Cited by 71 publications

References 45 publications

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

Structural and Electronic Properties of Pt13 Nanoclusters on Amorphous Silica Supports

Fast Prediction of Adsorption Properties for Platinum Nanocatalysts with Generalized Coordination Numbers

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Product

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Structural and Electronic Properties of Pt₁₃ Nanoclusters on Amorphous Silica Supports