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Lau K, Niemann F, Abdiaziz K, Heidelmann M, Yang Y, Tong Y, Fechtelkord M, Schmidt TC, Schnegg A, Campen RK, Peng B, Muhler M, Reichenberger S, Barcikowski S. Differentiating between Acidic and Basic Surface Hydroxyls on Metal Oxides by Fluoride Substitution: A Case Study on Blue TiO 2 from Laser Defect Engineering. Angew Chem Int Ed Engl 2023; 62:e202213968. [PMID: 36625361 DOI: 10.1002/anie.202213968] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/15/2022] [Accepted: 01/09/2023] [Indexed: 01/11/2023]
Abstract
Both oxygen vacancies and surface hydroxyls play a crucial role in catalysis. Yet, their relationship is not often explored. Herein, we prepare two series of TiO2 (rutile and P25) with increasing oxygen deficiency and Ti3+ concentration by pulsed laser defect engineering in liquid (PUDEL), and selectively quantify the acidic and basic surface OH by fluoride substitution. As indicated by EPR spectroscopy, the laser-generated Ti3+ exist near the surface of rutile, but appear to be deeper in the bulk for P25. Fluoride substitution shows that extra acidic bridging OH are selectively created on rutile, while the surface OH density remains constant for P25. These observations suggest near-surface Ti3+ are highly related to surface bridging OH, presumably the former increasing the electron density of the bridging oxygen to form more of the latter. We anticipate that fluoride substitution will enable better characterization of surface OH and its correlation with defects in metal oxides.
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Affiliation(s)
- Kinran Lau
- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141, Essen, Germany
| | - Felix Niemann
- Instrumental Analytical Chemistry, University of Duisburg-Essen, 45141, Essen, Germany
| | - Kaltum Abdiaziz
- EPR Research Group, Max Planck Institute for Chemical Energy Conversion, 45470, Mülheim an der Ruhr, Germany
| | | | - Yuke Yang
- Faculty of Physics, University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Yujin Tong
- Faculty of Physics, University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Michael Fechtelkord
- Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Torsten C Schmidt
- Instrumental Analytical Chemistry, University of Duisburg-Essen, 45141, Essen, Germany
| | - Alexander Schnegg
- EPR Research Group, Max Planck Institute for Chemical Energy Conversion, 45470, Mülheim an der Ruhr, Germany
| | - R Kramer Campen
- Faculty of Physics, University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Baoxiang Peng
- Laboratory of Industrial Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Martin Muhler
- Laboratory of Industrial Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Sven Reichenberger
- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141, Essen, Germany
| | - Stephan Barcikowski
- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141, Essen, Germany
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