Hydrogen Dissociation and Spillover on Individual Isolated Palladium Atoms

Tierney, Heather L.; Baber, Ashleigh E.; Kitchin, John R.; Sykes, E. Charles H.

doi:10.1103/physrevlett.103.246102

Cited by 239 publications

(355 citation statements)

References 29 publications

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“…16 Nevertheless, in the field of hydrogen storage, particular interest has been focused on carbon surfaces. Since porous carbon structures with large surface areas have commonly been synthesized, the feasibility of hydrogen spillover onto a carbon surface implies a potential breakthrough in room-temperature storage.…”

Section: B the Carbon Surface As A Receptormentioning

confidence: 99%

Stability of hydrogenation states of graphene and conditions for hydrogen spillover

Han

Jung

et al. 2012

Phys. Rev. B

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The hydrogen spillover mechanism has been discussed in the field of hydrogen storage and is believed to have particular advantage over the storage as metal or chemical hydrides. We investigate conditions for practicality realizing the hydrogen spillover mechanism onto carbon surfaces, using first-principles methods. Our results show that contrary to common belief, types of hydrogenation configurations of graphene (the aggregated all-paired configurations) can satisfy the thermodynamic requirement for room-temperature hydrogen storage. However, the peculiarity of the paired adsorption modes gives rise to a large kinetic barrier against hydrogen migration and desorption. It means that an extremely high pressure is required to induce the migration-derived hydrogenation. However, if mobile catalytic particles are present inside the graphitic interstitials, hydrogen migration channels can open and the spillover phenomena can be realized. We suggest a molecular model for such a mobile catalyst which can exchange hydrogen atoms with the wall of graphene.

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Section: B the Carbon Surface As A Receptormentioning

confidence: 99%

Stability of hydrogenation states of graphene and conditions for hydrogen spillover

Han

Jung

et al. 2012

Phys. Rev. B

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“…The use of a model system amenable to study by scanning tunnelling microscopy (STM) was critical in order to monitor the detailed distribution of Pd atoms, H a and CO molecules, all of which are distributed heterogeneously at the atomic-scale. This information can then be related to temperature programmed desorption/reaction (TPD/R) data, and complex phenomena like spillover, competitive adsorption and storage can be understood 12,[17][18][19][20] .It is well established that at low coverages (typically less than 0.1 monolayers (ML)), Pd atoms in the surface of Cu(111) exist predominantly as individual atoms that are isolated from one another [20][21][22][23] . For this reason we term this particular type of alloy a single atom alloy (SAA) 12 .…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…It is well established that at low coverages (typically less than 0.1 monolayers (ML)), Pd atoms in the surface of Cu(111) exist predominantly as individual atoms that are isolated from one another [20][21][22][23] . For this reason we term this particular type of alloy a single atom alloy (SAA) 12 .…”

mentioning

confidence: 99%

“…This information can then be related to temperature programmed desorption/reaction (TPD/R) data, and complex phenomena like spillover, competitive adsorption and storage can be understood 12,[17][18][19][20] .…”

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confidence: 99%

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Controlling a spillover pathway with the molecular cork effect

et al. 2013

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Spillover of reactants from one active site to another is important in heterogeneous catalysis and has recently been shown to enhance hydrogen storage in a variety of materials [1][2][3][4][5][6][7] . The spillover of hydrogen is notoriously hard to detect or control 1,2,4-6 . We report herein that the hydrogen spillover pathway on a Pd/Cu alloy can be controlled by reversible adsorption of a spectator molecule. Pd atoms in the Cu surface serve as hydrogen dissociation sites from which H atoms can spillover onto surrounding Cu regions. Selective adsorption of CO at these atomic Pd sites is shown to either prevent the uptake of hydrogen on, or inhibit its desorption from, the surface. In this way, the hydrogen coverage on the whole surface can be controlled by molecular adsorption at a minority site, which we term a "molecular cork" effect. We show that the molecular cork effect is present during a surface catalyzed hydrogenation reaction and illustrate how it can be used as a method for controlling uptake and release of hydrogen in a model storage system 1,2,[4][5][6]8 .Hydrogen activation, uptake, and reaction are important phenomena in heterogeneous catalysis, fuel cells, hydrogen storage devices, materials processing and sensing [1][2][3][4][5][6][7][8][9][10][11] . Much attention has been devoted to materials that exhibit facile activation and weak binding of hydrogen, as these properties lead to the best energy landscape for storage or chemical reactivity [12][13][14] . Spillover is a common method by which a reagent can be activated at one location and then reacted at another, and it is commonly invoked to explain the synergistic relationship between metals in an alloy or metal/metal oxide mixtures 1,[3][4][5][6][7]12,15 . For example, in heterogeneous catalysis hydrogen spillover from metal particles to reducible oxide supports is implicated as an important step in a variety of reactions including hydrogenations, hydroisomerizations, and methanol synthesis 1,3,6 . Hydrogen spillover has also been shown to significantly enhance the performance of hydrogen storage materials such as metal organic frameworks, zeolites and many carbon-based nanostructures 2,4-6 . In these cases, the addition of small metal particles, typically Pt or Pd, promotes uptake by activating molecular H 2 and facilitating spillover of hydrogen atoms (H a ) onto the support. Despite these advances, the mechanism of spillover in most systems remains poorly understood, and with the exception of hydrogen bridges 16 in storage systems, methods for mediating the spillover pathway do not exist. In this paper we describe how the hydrogen spillover pathway on the Pd/Cu alloy system can be controlled via the reversible adsorption of a spectator molecule (CO) at minority Pd atom sites. The use of a model system amenable to study by scanning tunnelling microscopy (STM) was critical in order to monitor the detailed distribution of Pd atoms, H a and CO molecules, all of which are distributed heterogeneously at the atomic-scale. This information ca...

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Single‐Metal Alloys

Han

Wang

2022

Supported Metal Single Atom Catalysis

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Hydrogen Dissociation and Spillover on Individual Isolated Palladium Atoms

Cited by 239 publications

References 29 publications

Stability of hydrogenation states of graphene and conditions for hydrogen spillover

Stability of hydrogenation states of graphene and conditions for hydrogen spillover

Controlling a spillover pathway with the molecular cork effect

Single‐Metal Alloys

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