Introduction of oxygen vacancies and fluorine into TiO{sub 2} nanoparticles by co-milling with PTFE

Journal Article · Thu Mar 15 04:00:00 EDT 2012 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2011.12.036· OSTI ID:22012038

Senna, Mamoru ^[1]; Sepelak, Vladimir ^[2]; Shi, Jianmin; Bauer, Benjamin ^[1]; Feldhoff, Armin ^[3]; Laporte, Vincent ^[4]; Becker, Klaus-Dieter ^[1]

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1. Institute of Physical and Theoretical Chemistry, Technische Universitaet Braunschweig, Braunschweig (Germany)
2. Institute of Nanotechnology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany)
3. Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Hannover (Germany)
4. Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO{sub 2} nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm{sup -1} (1140 nm) was attributed to the change in the electronic states, viz. electrons trapped at the oxygen vacancies (Vo) and d-d transitions of titanium ions. Incorporation of fluorine into n-TiO{sub 2} was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO{sub 2} was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO{sub 2} lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO{sub 6-n}Vo{sub n}, located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO{sub 2} particles, where local non-crystalline states predominate. - Graphical abstract: Scheme of the reaction processes: (a) pristine mixture, (b) oxygen abstraction from TiO{sub 2} and (c) fluorine migration from PTFE to TiO{sub 2}. Highlights: Transfer of fluorine from PTFE to n-TiO{sub 2} in a dry solid state process was confirmed. Black-Right-Pointing-Pointer 40% of F in PTFE was incorporated to the near surface region of n-TiO{sub 2} nanoparticles. Black-Right-Pointing-Pointer The transfer process is triggered by the oxidative decomposition of PTFE. Black-Right-Pointing-Pointer Fluorine incorporation is mediated by the formation of oxygen vacancies. Black-Right-Pointing-Pointer The sequential mechanisms are verified by XPS, EDXS, HRTEM, TG and DRS.

• OSTI ID: 22012038
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. . 187; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION
CRYSTALS
DECOMPOSITION
DIFFERENTIAL THERMAL ANALYSIS
FLUORINE
MILLING
NANOSTRUCTURES
OXIDATION
OXYGEN
PARTICLES
SOLIDS
SURFACES
TEFLON
TITANIUM IONS
TITANIUM OXIDES
TRANSMISSION ELECTRON MICROSCOPY
VACANCIES
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY
X-RAY SPECTROSCOPY