Elucidating the Roles of Amorphous Alumina Overcoat in Palladium-Catalyzed Selective Hydrogenation

Divakar R. Aireddy, Haoran Yu, David A. Cullen, Kunlun Ding

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Amorphous alumina overcoats generated by atomic layer deposition (ALD) have been shown to improve the selectivity and durability of supported metal catalysts in many reactions. Several mechanisms have been proposed to explain the enhanced catalytic performance, but the accessibilities of reactants through the amorphous overcoats remain elusive, which is crucial for understanding reaction mechanisms. Here, we show that an AlOxALD overcoat is able to improve the alkene product selectivity of a supported Pd catalyst in acetylene (C2H2) hydrogenation. We further demonstrate that the AlOxALD overcoat blocks the access of C2H2(kinetic diameter of 0.33 nm), O2(0.35 nm), and CO (0.38 nm) but allows H2(0.29 nm) to access Pd surfaces. A H-D exchange experiment suggests that H2might dissociate heterolytically at the Pd-AlOxinterface. These findings are in favor of a hydrogen spillover mechanism.

Original languageEnglish
Pages (from-to)24290-24298
Number of pages9
JournalACS Applied Materials and Interfaces
Volume14
Issue number21
DOIs
StatePublished - Jun 1 2022

Funding

The authors thank Dr. Spivey for access to the IR instrument. K.D. acknowledges the startup funding and LIFT2 Grant from Louisiana State University. Transmission electron microscopy and X-ray diffraction studies were performed at the Shared Instrumentation Facility (SIF) at Louisiana State University. Scanning transmission electron microscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Keywords

  • amorphous overcoat
  • atomic layer deposition
  • heterolytic hydrogen dissociation
  • hydrogen spillover
  • selective hydrogenation

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