Discriminating the Role of Surface Hydride and Hydroxyl for Acetylene Semihydrogenation over Ceria through in Situ Neutron and Infrared Spectroscopy

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Abstract

Ceria has been used as a hydrogenation catalyst especially in selective alkyne hydrogenation, but the reaction mechanism regarding the role of different surface hydrogen species remains unclear. In this work, we utilized in situ neutron and infrared vibration spectroscopy to show the catalytic role of cerium hydride (Ce-H) and hydroxyl (OH) groups in acetylene hydrogenation over ceria surfaces with different degree of reduction. In situ inelastic neutron scattering spectroscopy (INS) proved that not only Ce-H but also surface atomic hydrogen species on the reduced ceria surface can participate in acetylene semihydrogenation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results implied that bridging OH groups both on the oxidized and reduced ceria are active in the selective hydrogenation of acetylene. It appears that surface Ce-H is more reactive than the coexisting OH species on the reduced ceria surface, but over-reduction of ceria also results in strongly bound species that may lead to catalyst deactivation. These spectroscopic results clearly explain the reaction mechanism including not only the surface chemistry but also the nature of the active hydrogen species for selective hydrogenation over ceria, providing insights into the design of more active and stable ceria-based catalysts for hydrogenation reactions.

Original languageEnglish
Pages (from-to)5278-5287
Number of pages10
JournalACS Catalysis
Volume10
Issue number9
DOIs
StatePublished - May 1 2020

Funding

This research was sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science program. Part of the work including synthesis and IR spectroscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The neutron studies used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by ORNL. Notice: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Keywords

  • IR spectroscopy
  • acetylene
  • ceria
  • hydride
  • hydroxyl
  • inelastic neutron scattering
  • selective hydrogenation

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