Atomic-Scale View of Redox Induced Changes for Monolayer MoOx on α-TiO2(110) with Chemical-State Sensitivity

Michael J. Bedzyk*, Anusheela Das, Leighton O. Jones, Yanna Chen, Devika Choudhury, Denis T Keane, Jeffrey W. Elam, George C Schatz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Supported molybdenum oxide (MoOx) plays an important role in catalytic transformations from alcohol dehydrogenation to transesterification. During these reactions, molybdenum and oxygen surface species undergo structural and chemical changes. A detailed, chemical-state specific, atomic-scale structural analysis of the catalyst under redox conditions is important for improving catalytic properties. In this study, a monolayer of Mo grown on α-TiO2(110) by atomic-layer deposition is analyzed by X-ray standing wave (XSW) excited X-ray photoelectron spectroscopy (XPS). The chemical shifts for Mo 2p3/2 and O 1s peaks are used to distinguish Mo6+ from Mo4+ and surface O from bulk O. Excitation of XPS by XSW allows pinpointing the location of these surface species relative to the underlying substrate lattice. Measured 3D composite atomic density maps for the oxidized and reduced interfaces compare well with our density functional theory models and collectively create a unique view of the redox-driven dynamics for this complex catalytic structure.

Original languageEnglish (US)
Pages (from-to)5304-5309
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume13
Issue number23
DOIs
StatePublished - Jun 16 2022

Funding

This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, ICEP program, under Award DE-FG02-03ER15457. This work made use of the Keck-II facility and SPID facility of Northwestern University’s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), IIN, and Northwestern’s MRSEC program (NSF DMR-1720139). This XSW-XPS work used DND-CAT at the Advanced Photon Source (APS). DND-CAT is supported through E. I. DuPont de Nemours & Co., Northwestern University, The Dow Chemical Co., and the NSF funded MRSEC at NU. The ALD and use of the APS at Argonne National Lab are funded by DOE (DE-AC02-06CH11357). We thank James Rix (NU) and Dr. Mike Guise (NU) for assistance with our beamtime at APS. We thank Dr. Anil Mane (ANL) for his help with ALD growth and Prof. Justin Notestein (NU) for helpful scientific discussions. The theory research was supported in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry

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