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Zhu Q, Adachi Y, Wen H, Xu R, Cheng Z, Sugawara Y, Li Y. Charge State of Au Atoms on an Oxidized Rutile TiO 2(110) Surface by AFM/KPFM at 78 K. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:1358-1363. [PMID: 38174984 DOI: 10.1021/acs.langmuir.3c02999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
The charge state of noble metal atoms on a semiconductor surface is an important factor in surface catalysis. In this study, Au atoms were deposited on the rutile TiO2(110) surface to characterize its charge properties using atomic force microscopy with Kelvin probe force microscopy at 78 K. Au single atoms, dimers, and trimers at different sites on the surface were investigated. Positively charged Au atoms were verified at oxygen sites, while negatively charged Au atoms were found near oxygen vacancy sites. Furthermore, the charge states of small Au nanoclusters were clarified. Understanding the charge states of Au atoms is significant for identifying their efficient catalytic effects in surface catalysis.
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Affiliation(s)
- Qiang Zhu
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan
| | - Yuuki Adachi
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan
| | - Huanfei Wen
- Key Laboratory of Instrumentation Science and Dynamic Measurement, School of Instrument and Electronics, North University of China, Taiyuan, Shanxi 030051, People's Republic of China
| | - Rui Xu
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Zhihai Cheng
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Yasuhiro Sugawara
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan
| | - Yanjun Li
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan
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Sombut P, Puntscher L, Atzmueller M, Jakub Z, Reticcioli M, Meier M, Parkinson GS, Franchini C. Role of Polarons in Single-Atom Catalysts: Case Study of Me 1 [Au 1, Pt 1, and Rh 1] on TiO 2(110). Top Catal 2022; 65:1620-1630. [PMID: 36405974 PMCID: PMC9668789 DOI: 10.1007/s11244-022-01651-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2022] [Indexed: 11/29/2022]
Abstract
The local environment of metal-oxide supported single-atom catalysts plays a decisive role in the surface reactivity and related catalytic properties. The study of such systems is complicated by the presence of point defects on the surface, which are often associated with the localization of excess charge in the form of polarons. This can affect the stability, the electronic configuration, and the local geometry of the adsorbed adatoms. In this work, through the use of density functional theory and surface-sensitive experiments, we study the adsorption of Rh1, Pt1, and Au1 metals on the reduced TiO2(110) surface, a prototypical polaronic material. A systematic analysis of the adsorption configurations and oxidation states of the adsorbed metals reveals different types of couplings between adsorbates and polarons. As confirmed by scanning tunneling microscopy measurements, the favored Pt1 and Au1 adsorption at oxygen vacancy sites is associated with a strong electronic charge transfer from polaronic states to adatom orbitals, which results in a reduction of the adsorbed metal. In contrast, the Rh1 adatoms interact weakly with the excess charge, which leaves the polarons largely unaffected. Our results show that an accurate understanding of the properties of single-atom catalysts on oxide surfaces requires a careful account of the interplay between adatoms, vacancy sites, and polarons. Supplementary Information The online version contains supplementary material available at 10.1007/s11244-022-01651-0.
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Affiliation(s)
| | - Lena Puntscher
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | | | - Zdenek Jakub
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
| | - Michele Reticcioli
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, 1090 Vienna, Austria
| | - Matthias Meier
- Institute of Applied Physics, TU Wien, 1040 Vienna, Austria
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, 1090 Vienna, Austria
| | | | - Cesare Franchini
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, 1090 Vienna, Austria
- Alma Mater Studiorum, Università di Bologna, 40127 Bologna, Italy
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Qi P, Wang J, Djitcheu X, He D, Liu H, Zhang Q. Techniques for the characterization of single atom catalysts. RSC Adv 2021; 12:1216-1227. [PMID: 35425093 PMCID: PMC8978979 DOI: 10.1039/d1ra07799f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/17/2021] [Indexed: 12/17/2022] Open
Abstract
Single atom catalysts (SACs) are a hot research area recently. Over most of the SACs, the singly dispersed atoms are the active sites, which contribute to the catalytic activities significantly compared with a catalyst with continuously packed active sites. It is essential to determine whether SACs have been successfully synthesized. Several techniques have been applied for the characterization of the dispersion states of the active sites over SACs, such as Energy Dispersive X-ray spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS), etc. In this review, the techniques for the identification of the singly dispersed sites over SACs are introduced, the advantages and limitations of each technique are pointed out, and the future research directions have been discussed. It is hoped that this review will be helpful for a more comprehensive understanding of the characterization and detection methods involved in SACs, and stimulate and promote the further development of this emerging research field.
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Affiliation(s)
- Ping Qi
- School of Chemical and Environmental Engineering, Liaoning University of Technology Jinzhou 121001 P. R. China
| | - Jian Wang
- School of Chemical and Environmental Engineering, Liaoning University of Technology Jinzhou 121001 P. R. China
| | - Xavier Djitcheu
- School of Chemical and Environmental Engineering, Liaoning University of Technology Jinzhou 121001 P. R. China
| | - Dehua He
- Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Huimin Liu
- School of Chemical and Environmental Engineering, Liaoning University of Technology Jinzhou 121001 P. R. China
| | - Qijian Zhang
- School of Chemical and Environmental Engineering, Liaoning University of Technology Jinzhou 121001 P. R. China
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Yim CM, Lamoureux PS, Mellor A, Pang CL, Idriss H, Pacchioni G, Thornton G. Size and Shape Dependence of the Electronic Structure of Gold Nanoclusters on TiO 2. J Phys Chem Lett 2021; 12:8363-8369. [PMID: 34432476 DOI: 10.1021/acs.jpclett.1c02167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding the mechanism behind the superior catalytic power of single- or few-atom heterogeneous catalysts has become an important topic in surface chemistry. This is particularly the case for gold, with TiO2 being an efficient support. Here we use scanning tunneling microscopy/spectroscopy with theoretical calculations to investigate the adsorption geometry and local electronic structure of several-atom Au clusters on rutile TiO2(110), with the clusters fabricated by controlled manipulation of single atoms. Our study confirms that Au1 and Au2 clusters prefer adsorption at surface O vacancies. Au3 clusters adsorb at O vacancies in a linear-chain configuration parallel to the surface; in the absence of O vacancies they adsorb at Ti5c sites with a structure of a vertically pointing upright triangle. We find that both the electronic structure and cluster-substrate charge transfer depend critically on the cluster size, bonding configuration, and local environment. This suggests the possibility of engineering cluster selectivity for specific catalytic reactions.
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Affiliation(s)
- Chi-Ming Yim
- Department of Chemistry and London Centre for Nanotechnology, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Philomena Schlexer Lamoureux
- Dipartimento di Scienza dei Materiali, Università degli Studi Milano-Bicocca, via R. Cozzi 55, 20126 Milano, Italy
| | - Andrew Mellor
- Department of Chemistry and London Centre for Nanotechnology, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Chi L Pang
- Department of Chemistry and London Centre for Nanotechnology, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Hicham Idriss
- Surface Science and Advanced Characterisation, Chemical Sciences Division, SABIC-CRD at KAUST, Thuwal 23955, Saudi Arabia
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università degli Studi Milano-Bicocca, via R. Cozzi 55, 20126 Milano, Italy
| | - Geoff Thornton
- Department of Chemistry and London Centre for Nanotechnology, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
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