4.7 Article

Dielectric Properties and Spectral Characteristics of Photocatalytic Constant of TiO2 Nanoparticles Doped with Cobalt

Journal

NANOMATERIALS
Volume 11, Issue 10, Pages -

Publisher

MDPI
DOI: 10.3390/nano11102519

Keywords

photocatalysis; nanomaterials; dielectric properties; titanium dioxide

Funding

  1. Center of Marine Science (CCMAR) in Algarve University
  2. Fundacao para a Ciencia e a Tecnologia (FCT), Portugal [UIDB/00100/2020]
  3. FCT, Portugal [UID/NAN/50024/2013]
  4. ERASMUS+ program in Rostock University
  5. Physics Department of the Faculty of Science and Technology in Algarve University

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The dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. The research showed a concentration limit for cobalt distribution in the TiO2 matrix before metallic clusters form, and the formation of CoTiO3 phases during annealing at high temperatures. The temperature dependence of the dielectric constant indicated relaxation processes at temperatures below 400 degrees C and Ti-O octahedron reorientation at higher temperatures. The spectral dependency of the photocatalytic constant revealed the presence of electronic states within the energy gap of TiO2 for all nanopowdered samples.
Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc-Co[(C2H5)(2)NCS2](3)). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO2:Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO2:0.1Co) where cobalt atoms can be uniformly distributed across the TiO2 matrix before metallic clusters start to form. It was also shown that CoTiO3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 degrees C and that oxygen defect Ti-O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO2 for all nanopowdered samples.

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