Turning aluminium into a noble-metal-like catalyst for low-temperature activation of molecular hydrogen

Chopra, Irinder S.; Chaudhuri, Santanu; Veyan, Jean-François; Chabal, Yves J.

doi:10.1038/nmat3123

Cited by 44 publications

(55 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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 .…”

mentioning

confidence: 99%

Controlling a spillover pathway with the molecular cork effect

et al. 2013

View full text Add to dashboard Cite

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...

show abstract

mentioning

confidence: 99%

Controlling a spillover pathway with the molecular cork effect

et al. 2013

View full text Add to dashboard Cite

show abstract

“…18 The reported system can effectively activate molecular hydrogen similarly to catalysts with precious elements. Chabal and co-workers reported an aluminium catalyst doped with very small amounts of titanium that were subjected to detailed analyses of atomic process on the surfaces using infrared reflectionadsorption spectroscopy and first-principles simulations.…”

Section: Hideki Abementioning

confidence: 96%

Atomic architectonics, nanoarchitectonics and microarchitectonics for strategies to make junk materials work as precious catalysts

2016

View full text Add to dashboard Cite

In order to solve problems of limited resources and their unbalanced distributions, considerable efforts to replace precious elements with naturally abundant elements have been made using various approaches. In this highlight article, we briefly introduce several recent examples of the use of earth-abundant elements for producing environmentally friendly catalysts with performance efficiencies comparable to those made from precious metals on the basis of three types of architectonics: atomic architectonics, nanoarchitectonics, and microarchitectonics. Atomic architectonics has been applied to make highly efficient catalysts of the activation of molecular hydrogen, NO oxidation, and photo-driven water splitting with inexpensive elements through well-considered combinations and compositions of these elements. Applying nanoarchitectonics to control lattice features and produce hierarchical arrangements of "junk" materials such as CuO have made these materials catalyze the consumption of NO better than Pt catalysts and as well as Rh catalysts. Larger-scale control of morphology by applying microarchitectonics has been used to effectively avoid the agglomeration of catalyst particles and hence suppress the degradation of these catalysts as well as to minimize the use of precious-element catalysts.

show abstract

“…However,i ftheHcoverage is high and the surfaceA lc an be continuously consumed, Ti tends to segregate to the surface and form as trong bond with the H. As reported by ar ecent study [29] of aT i-doped Al(111)s urface as ap otential heterogeneous catalyst for hydrogenation reactions,i th as been found that the adsorption of Ha nd CO keeps Ti in the surfacel ayer. Conversely,t he self-diffusion barrierf or an Al adatom on Al(111)i so nly [30] approximately 0.04 eV,m uch smaller than the barrierf or Hd iffusion [24,31] (0.15 eV), or Hs pillover from subsur-Alane (AlH 3 )i saunique energetic material that has not found ab road practical use for over 70 years because it is difficult to synthesize directly from its elements.…”

Section: Introductionmentioning

confidence: 95%

“…Some studies [22,24,26] have proposed that subsurface Ti can be more active than surface Ti in alane formation because of the lower barrier for H-spillover to Al by avoiding the formation of strong Ti-H bonds that hinder alane formation. However, when H-coverage is high and the surface Al can be continuously consumed, Ti tends to segregate to the surface and form a strong bond with the H. As reported by a recent study [29] of a Ti-doped Al(111) surface as a potential heterogeneous catalyst for hydrogenation reactions, it has been found that the adsorption of H and CO keeps Ti in the surface layer. On the other hand, the self-diffusion barrier for an Al adatom on Al(111) is only [30] ~0.04 eV, much smaller than the barrier for H-diffusion [24,31] (0.15 eV), or H-spillover from subsurface Ti (0.23 eV) [22] and surface Ti (0.7 eV [24] to 0.9 eV [22] ).…”

Section: Introductionmentioning

confidence: 95%

Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

et al. 2016

View full text Add to dashboard Cite

Alane (AlH3) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defectmediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H2 exposure, alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 104 bar expected from bulk thermodynamics. [d,f] S. Gupta, [a] and V. K. Pecharsky* [a,c] Abstract: Alane (AlH3) is a unique energetic material that has not found broad practical use for over 70 years due to difficulties of its direct synthesis from elements. Using density functional theory we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation; both are endothermic on clean surface. Only with Ti-dopant to facilitate H2 dissociation and vacancy to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunnelling microscopy showed that during H2 exposure alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball-milling samples of Al with Ti (providing necessary defects) showed a 10% conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to direct synthesis of alane from elements at pressures much lower than the 10 4 bar expected from bulk thermodynamics.

show abstract

Turning aluminium into a noble-metal-like catalyst for low-temperature activation of molecular hydrogen

Cited by 44 publications

References 33 publications

Controlling a spillover pathway with the molecular cork effect

Controlling a spillover pathway with the molecular cork effect

Atomic architectonics, nanoarchitectonics and microarchitectonics for strategies to make junk materials work as precious catalysts

Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

Contact Info

Product

Resources

About