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Jiang Y, Zhu Y, Zhou D, Jiang Z, Si N, Stacchiola D, Niu T. Reversible oxidation and reduction of gold-supported iron oxide islands at room temperature. J Chem Phys 2020; 152:074710. [PMID: 32087652 DOI: 10.1063/1.5136279] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Monolayer iron oxides grown on metal substrates have widely been used as model systems in heterogeneous catalysis. By means of ambient-pressure scanning tunneling microscopy (AP-STM), we studied the in situ oxidation and reduction of FeO(111) grown on Au(111) by oxygen (O2) and carbon monoxide (CO), respectively. Oxygen dislocation lines present on FeO islands are highly active for O2 dissociation. X-ray photoelectron spectroscopy measurements distinctly reveal the reversible oxidation and reduction of FeO islands after sequential exposure to O2 and CO. Our AP-STM results show that excess O atoms can be further incorporated on dislocation lines and react with CO, whereas the CO is not strong enough to reduce the FeO supported on Au(111) that is essential to retain the activity of oxygen dislocation lines.
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Affiliation(s)
- Yixuan Jiang
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei 210094, China
| | - Yaguang Zhu
- Center for Functional Nanomaterials, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000, USA
| | - Dechun Zhou
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei 210094, China
| | - Zhao Jiang
- Department of Chemical Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Nan Si
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei 210094, China
| | - Dario Stacchiola
- Center for Functional Nanomaterials, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000, USA
| | - Tianchao Niu
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei 210094, China
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Asundi AS, Hoffman AS, Bothra P, Boubnov A, Vila FD, Yang N, Singh JA, Zeng L, Raiford JA, Abild-Pedersen F, Bare SR, Bent SF. Understanding Structure-Property Relationships of MoO 3-Promoted Rh Catalysts for Syngas Conversion to Alcohols. J Am Chem Soc 2019; 141:19655-19668. [PMID: 31724857 DOI: 10.1021/jacs.9b07460] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rh-based catalysts have shown promise for the direct conversion of syngas to higher oxygenates. Although improvements in higher oxygenate yield have been achieved by combining Rh with metal oxide promoters, details of the structure of the promoted catalyst and the role of the promoter in enhancing catalytic performance are not well understood. In this work, we show that MoO3-promoted Rh nanoparticles form a novel catalyst structure in which Mo substitutes into the Rh surface, leading to both a 66-fold increase in turnover frequency and an enhancement in oxygenate yield. By applying a combination of atomically controlled synthesis, in situ characterization, and theoretical calculations, we gain an understanding of the promoter-Rh interactions that govern catalytic performance for MoO3-promoted Rh. We use atomic layer deposition to modify Rh nanoparticles with monolayer-precise amounts of MoO3, with a high degree of control over the structure of the catalyst. Through in situ X-ray absorption spectroscopy, we find that the atomic structure of the catalytic surface under reaction conditions consists of Mo-OH species substituted into the surface of the Rh nanoparticles. Using density functional theory calculations, we identify two roles of MoO3: first, the presence of Mo-OH in the catalyst surface enhances CO dissociation and also stabilizes a methanol synthesis pathway not present in the unpromoted catalyst; and second, hydrogen spillover from Mo-OH sites to adsorbed species on the Rh surface enhances hydrogenation rates of reaction intermediates.
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Affiliation(s)
- Arun S Asundi
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Adam S Hoffman
- SSRL , SLAC National Accelerator Laboratory , Menlo Park , California 94205 , United States
| | - Pallavi Bothra
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States.,SUNCAT Center for Interface Science and Catalysis , SLAC National Accelerator Laboratory , Menlo Park , California 94205 , United States
| | - Alexey Boubnov
- SSRL , SLAC National Accelerator Laboratory , Menlo Park , California 94205 , United States
| | - Fernando D Vila
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
| | - Nuoya Yang
- Department of Materials Science and Engineering , Stanford University , Stanford , California 94305 , United States
| | - Joseph A Singh
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Li Zeng
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States
| | - James A Raiford
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Frank Abild-Pedersen
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States.,SUNCAT Center for Interface Science and Catalysis , SLAC National Accelerator Laboratory , Menlo Park , California 94205 , United States
| | - Simon R Bare
- SSRL , SLAC National Accelerator Laboratory , Menlo Park , California 94205 , United States
| | - Stacey F Bent
- Department of Chemical Engineering , Stanford University , Stanford , California 94305 , United States
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