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Parker SF, Walker HC, Callear SK, Grünewald E, Petzold T, Wolf D, Möbus K, Adam J, Wieland SD, Jiménez-Ruiz M, Albers PW. The effect of particle size, morphology and support on the formation of palladium hydride in commercial catalysts. Chem Sci 2019; 10:480-489. [PMID: 30713645 PMCID: PMC6334263 DOI: 10.1039/c8sc03766c] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 10/15/2018] [Indexed: 11/24/2022] Open
Abstract
The influence of the support on the quantity of hydrogen present in a supported palladium catalyst is characterised. The on-top hydrogen on β-PdH is observed for the first time.
The relative amounts of hydrogen retained by a range of supported palladium catalysts have been investigated by a combination of electron microscopy and spectroscopic techniques, including incoherent inelastic neutron scattering. Contrary to expectation, the hydrogen capacity is not determined solely by the metal particle size, but it is a complex interaction between the particle size and its state of aggregation. The nature of the support is not only integral to the amount of hydrogen held by the catalyst, it also causes a marked difference in the rate of release of stored hydrogen from palladium. It is more difficult to fully dehydrogenate palladium on/in the porous activated carbon than on the non-porous carbon black based catalyst. The type of support also results in differences in the form of the residual hydrogen: whether it is α- or β-hydride phase, subsurface or in the threefold surface site. Our data on the supported catalysts reinforces what has only been seen previously with palladium black and our computational study provides confirmation of the empirical assignments. We also report the first vibrational spectroscopic study of hydrogen adsorbed at the surface of β-PdH and have observed for the first time hydrogen in the on-top site. This has enabled the relative proportion of bulk- to surface-H occupation in calculated model and in industrial nanoparticles to be estimated.
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Affiliation(s)
- Stewart F Parker
- ISIS Facility , STFC Rutherford Appleton Laboratory , Chilton , Didcot , OX11 0QX , UK .
| | - Helen C Walker
- ISIS Facility , STFC Rutherford Appleton Laboratory , Chilton , Didcot , OX11 0QX , UK .
| | - Samantha K Callear
- ISIS Facility , STFC Rutherford Appleton Laboratory , Chilton , Didcot , OX11 0QX , UK .
| | - Elena Grünewald
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Tina Petzold
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Dorit Wolf
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Konrad Möbus
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Julian Adam
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Stefan D Wieland
- Evonik Resource Efficiency GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany
| | - Mónica Jiménez-Ruiz
- Institut Laue-Langevin , 71 Avenue des Martyrs , CS 20156 38042 Grenoble Cedex 9 , France
| | - Peter W Albers
- Evonik Technology and Infrastructure GmbH , Rodenbacher Chaussee 4 , D-63457 Hanau-Wolfgang , Germany .
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Fernandez-Torres LC, Sykes ECH, Nanayakkara SU, Weiss PS. Dynamics and Spectroscopy of Hydrogen Atoms on Pd{111}. J Phys Chem B 2006; 110:7380-4. [PMID: 16599513 DOI: 10.1021/jp055815e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Chemisorption of hydrogen on Pd{111} is a relatively simple, yet important surface chemical process. By using low-temperature scanning tunneling microscopy, tip-induced motion of adsorbed atomic hydrogen at 4 K has been observed at low coverage. The motion has been ascribed to excitation of vibrational modes that decay into translational modes; vibrational spectroscopy via inelastic electron tunneling corroborates this assignment, and the barrier to hydrogen atom motion has been determined. At higher coverages, tip-induced motion of vacancies in the hydrogen overlayer is observed, and the associated barrier has also been determined.
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Affiliation(s)
- Luis C Fernandez-Torres
- Departments of Chemistry and Physics, 104 Davey Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802-6300
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Affiliation(s)
- Matthew Dyer
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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Albers PW, Krauter JGE, Ross DK, Heidenreich RG, Köhler K, Parker SF. Identification of surface states on finely divided supported palladium catalysts by means of inelastic incoherent neutron scattering. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:8254-8260. [PMID: 15350100 DOI: 10.1021/la040054c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The purpose of the present investigation was to utilize the inelastic incoherent neutron scattering (INS) technique to reveal changes at the surface of technical catalysts under the influence of hydrogen in gas/solid interactions and during chemical reactions in a liquid-phase process. The formation and the properties of supported palladium hydride and changes of the hydrogen-related surface chemistry of the corresponding activated carbon supports in 20% Pd/C catalysts after short-term and long-term hydrogen cycling at different hydrogen pressures and temperatures were studied. The spectra indicate that hydrogenation of the activated carbon support by hydrogen spillover occurs to, partly, give a material that strongly resembles a-C:H (amorphous hydrogenated carbon). Indications for different relaxation phenomena and long-range phase coherence inside of supported particles of palladium hydride compared to hydrogenated palladium black were obtained. A 5% Pd/C catalyst after use in C-C coupling reactions, the Heck reaction of bromobenzene and styrene to stilbenes, was also studied after subsequent solvent extraction. Evidence for a preferential adsorption and accumulation of cis-stilbene at the catalyst surface was obtained. INS allows identification of a certain isomer from a complex reaction mixture preferentially adsorbed at the surface of a finely divided industrial heterogeneous catalyst.
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Affiliation(s)
- Peter W Albers
- Degussa AG, Wolfgang Industrial Site, Department of Physical Chemistry, 63457 Hanau, Germany.
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