Differentiating between Acidic and Basic Surface Hydroxyls on Metal Oxides by Fluoride Substitution: A Case Study on Blue TiO2 from Laser Defect Engineering |
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| Authors: | Kinran Lau Felix Niemann Dr Kaltum Abdiaziz Dr Markus Heidelmann Yuke Yang Dr Yujin Tong Dr Michael Fechtelkord Prof Torsten C Schmidt Dr Alexander Schnegg Prof R Kramer Campen Dr Baoxiang Peng Prof Martin Muhler Dr Sven Reichenberger Prof Stephan Barcikowski |
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| Institution: | 1. Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany;2. Instrumental Analytical Chemistry, University of Duisburg-Essen, 45141 Essen, Germany;3. EPR Research Group, Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany;4. ICAN, University of Duisburg-Essen, 47057 Duisburg, Germany;5. Faculty of Physics, University of Duisburg-Essen, 47057 Duisburg, Germany;6. Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany;7. Laboratory of Industrial Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, 44780 Bochum, Germany |
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| 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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| Keywords: | Laser Chemistry Nanoparticles Oxygen Vacancy Titania Titration |
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