Investigating the Reactivity of Single Atom Alloys Using Density Functional Theory

Thirumalai, Hari; Kitchin, John R.

doi:10.1007/s11244-018-0899-0

Cited by 146 publications

(202 citation statements)

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“…This finding is important because research increasingly addresses nano-sized systems and clusters and even singleatom catalytic systems where d-band considerations are inappropriate. [20,22,77] Finding simple descriptors of metal reactivity and nobleness that apply to all scales and thermodynamic states is thus very desirable. In the view of the findings, it is tempting to relate the particular nobleness of bulk metal states to their higher electronegativity caused by the re-hybridization of the metal-metal bonds: Indeed metal atoms on exposed parts of surfaces and clusters tend to be substantially less electronegative simply because they engage less in electronstabilizing bonding orbital formation.…”

Section: Resultsmentioning

confidence: 99%

Chemical Causes of Metal Nobleness

Kepp

2020

ChemPhysChem

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Humans have appreciated the “noble” metals for millennia, yet modern chemistry still struggles with different definitions. Herein, metal nobleness is analyzed using thermochemical cycles including the different bulk, gas, and solution states implied by these definitions. The analysis suggests that metal nobleness mainly reflects inability to fulfil the electron demands of electronegative oxygen. Accordingly, gold is the most noble metal in existence, not because of d‐band properties of the solid state, but because gold's electronegativity is closest to that of oxygen, producing weaker polar covalent bonding. The high electronegativity arises from the effective nuclear charge due to diffuse d‐states, enforced by relativistic effects. This explanation accounts for the activity series, corrosion tendency, and trends in oxygen chemisorption, which other models do not. While gold is the most noble metal, the ranking of Ag, Pt, and Pd depends on the thermochemistry as discussed in detail.

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Section: Resultsmentioning

confidence: 99%

Chemical Causes of Metal Nobleness

Kepp

2020

ChemPhysChem

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“…79 Most recently, simulation using DFT has become more exploratory. 53,[90][91][92] Progress in applying theory and simulation to SAA systems has now reached a pivotal point where it is not only being used to explain experimental findings, but to make predictions. Thus, in the remainder of this Perspective, we will give a summary of key recent studies that provide insight into the structural stability, electronic structure and chemical reactivity of numerous SAAs yet to be experimentally synthesized and tested.…”

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confidence: 99%

“…In particular, Thirumalai et al have shown that the atom-projected d-band density of states (PDOS) graphs of SAA surfaces, generally exhibit a sharp peak of high population over a narrow energy span close to the Fermi level. 92 This feature in the PDOS is the result of a charge localization and ineffective charge mixing between the two metals in the alloy. 92 The peak is unusually sharp, even for an alloy system, and in fact is more akin to that found in the PDOS of an isolated gas phase atom, rather than an extended metallic surface.…”

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“…92 This feature in the PDOS is the result of a charge localization and ineffective charge mixing between the two metals in the alloy. 92 The peak is unusually sharp, even for an alloy system, and in fact is more akin to that found in the PDOS of an isolated gas phase atom, rather than an extended metallic surface. 92 This atom-like PDOS feature is thought to be responsible for the high surface reactivity of SAA dopant atoms.…”

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confidence: 99%

“…53,90 Interestingly for SAAs, the host-like or dopant-like strength of the bonding is not generally discerned through some linear combination of pure-host or pure-dopant adsorption energies, [96][97][98] nor do these surfaces adhere to the d-band adsorption model. 53,92 This makes SAA catalysts novel and exciting; by not following the scaling models of other pure and alloy transition metal surfaces, SAAs can offer unique adsorption properties that, when understood, can be employed in the design of superior catalysts. 53 The high dilution of isolated dopant atoms in SAA surfaces gives rise to several unique adsorption site types with varying properties.…”

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Lonely Atoms with Special Gifts: Breaking Linear Scaling Relationships in Heterogeneous Catalysis with Single-Atom Alloys

Darby

Stamatakis

Michaelides

et al. 2018

J. Phys. Chem. Lett.

238

274

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We discuss a simple yet effective strategy for escaping traditional linear scaling relations in heterogeneous catalysis with highly dilute bimetallic alloys known as single-atom alloys (SAAs). These systems, in which a reactive metal is atomically dispersed in a less reactive host, were first demonstrated with the techniques of surface science to be active and selective for hydrogenation reactions. Informed by these early results, PdCu and PtCu SAA nanoparticle hydrogenation catalysts were shown to work under industrially relevant conditions. To efficiently survey the many potential metal combinations and reactions, simulation is crucial for making predictions about reactivity and guiding experimental focus on the most promising candidate materials. This recent work reveals that the high surface chemical heterogeneity of SAAs can result in significant deviations from Brønsted-Evans-Polanyi scaling relationships for many key reaction steps. These recent insights into SAAs and their ability to break linear scaling relations motivate discovery of novel alloy catalysts.

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Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

et al. 2020

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between the electronic structure and catalytic efficiency of heterogenous catalysts. Dating back to 1930s, the concept of "electronic factor" was proposed by G. M. Schwab to describe the influence of electronic interaction on catalytic behavior of supported catalyst and divided the interaction into two parts, structural and synergetic ones. [4] Electrons transferring between the metal and the support was first under consideration when it came to the catalysis. After that, S. J. Tauster used the term of "strong metal-support interaction" (SMSI) to describe the chemisorption properties of group VIII elements supported by a metal oxide (e.g. SiO 2 , MgO) in 1978. [5] Later the concept was broadened to interaction between any metallic species and support, based on the experimental phenomena. [6] Till that time, based on the early characterization of surface science, researchers had realized that the active site might change during the process from metallic to an SMSI state, which was indicated to be covered or encapsulated by the support. [7] Among many hypotheses concerning the mechanism of SMSI, electron transfer between the metal and the support has been adapted by many researchers, and was confirmed by Rodriguez based on X-ray crystallography and UV photoemission spectroscopy in 1990s. [8] Then almost at the same time that the term of SACs was formally put forward, C. T. Campbell proposed the concept of "electronic metal-support interaction" (EMSI). As Campbell described, the chemical and catalytic properties might be affected by the electronic perturbations (i.e., shifts in the energy of d-band center) due to the EMSI. [9] In other words, the EMSI gave a much more detailed explanation of the enhanced properties of supported catalysts than SMSI, indicating that the study on catalysis was finally pushed to the electronic scale after so many years. [9b,c,10] Unfortunately, for metal particles or clusters, the accurate identification of electronic state is often difficult or even impossible. [11] The most reliable way to overcome the barrier above is to develop the catalyst based on single-atom metal that avoids intrinsic metal effects, including the electronic quantum size effect as well as structure-sensitivity geometrical effect. [12] Therefore, the rise of SACs provides a nearly perfect model to study the EMSI. As the supported metal species downsize to the single atom, the interaction between active site and support is always uniform, which can be much easier to be characterized by both experiment and theoretical calculation. [13] With the help of advanced techniques, for instance, X-ray absorption spectroscopy (XAS), the information about electronic The electronic metal-support interaction (EMSI), which acts as a bridge between theoretical electronic study and the design of heterogenous catalysts, has attracted much attention. Utilizing the interaction between the metal and the support is one of the most essential strategies to enhance electrocatalytic efficiency due to structural and synergetic promotion. To ...

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Investigating the Reactivity of Single Atom Alloys Using Density Functional Theory

Cited by 146 publications

References 54 publications

Chemical Causes of Metal Nobleness

Chemical Causes of Metal Nobleness

Lonely Atoms with Special Gifts: Breaking Linear Scaling Relationships in Heterogeneous Catalysis with Single-Atom Alloys

Electronic Metal–Support Interaction of Single‐Atom Catalysts and Applications in Electrocatalysis

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