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Unveiling Temperature-Mediated Dual-Band Edge in TiO2 Nanotubes with Enhanced Photocatalytic Effect

  • S. Bhowmick
    S. Bhowmick
    Department of Physics, School of Natural Sciences, Shiv Nadar University, NH-91, Tehsil Dadri, Gautam Buddha Nagar 201314, Uttar Pradesh, India
    More by S. Bhowmick
  • R. Sen*
    R. Sen
    Department of Physics, School of Natural Sciences, Shiv Nadar University, NH-91, Tehsil Dadri, Gautam Buddha Nagar 201314, Uttar Pradesh, India
    *Email: [email protected] (R.S.)
    More by R. Sen
  • C. P. Saini
    C. P. Saini
    Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India
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  • R. Singhal
    R. Singhal
    Department of Physics, Malaviya National Institute of Technology Jaipur, JLN Marg, Malaviya Nagar 302017, Jaipur, India
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  • L. Walczak
    L. Walczak
    Science & Research Division, PREVAC sp. z o.o., Raciborska 61, Rogow 44-362, Poland
    More by L. Walczak
  • M. Gupta
    M. Gupta
    UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh, India
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  • D. M. Phase
    D. M. Phase
    UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh, India
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  • , and 
  • A. Kanjilal*
    A. Kanjilal
    Department of Physics, School of Natural Sciences, Shiv Nadar University, NH-91, Tehsil Dadri, Gautam Buddha Nagar 201314, Uttar Pradesh, India
    *Email: [email protected] (A.K.)
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Cite this: J. Phys. Chem. C 2021, 125, 8, 4846–4859
Publication Date (Web):February 17, 2021
https://doi.org/10.1021/acs.jpcc.0c11081
Copyright © 2021 American Chemical Society
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Abstract

An annealing temperature-driven appearance of a sharp dual-band edge in the ultraviolet–visible absorption spectrum of electrochemically anodized TiO2 nanotubes (TNTs) and the corresponding impact on the photodegradation of organic dyes is reported based on the evolution of an anatase (A)/rutile (R) phase junction. Systematic X-ray diffraction followed by a micro-Raman analysis illustrates the impact of annealing between 500 and 900 °C in promoting the anatase-to-rutile phase transformation with a higher degree of crystallinity through an evolution of an intermediate mixed phase. X-ray photoelectron spectroscopy (XPS) further reveals a clear transition from the sub-stoichiometric to stoichiometric TNTs with increasing annealing temperature. Moreover, the valence band (VB) XPS along with the ultraviolet photoelectron spectroscopy (UPS) analysis suggests the possible band alignment at the A/R interface, whereas the X-ray absorption spectroscopy (XAS) at the Ti L- and O K-edges confirms a systematic change from an anatase to a rutile phase owing to the modification in local symmetry. To validate our experimental results, especially the formation of a dual-band edge at the A/R phase junction in TNTs, theoretical calculations using density functional theory (DFT) were also performed. Here, a one-to-one analysis of our theoretical and experimental results not only shows a good agreement to each other but also illustrates the microscopic origin behind the formation of a dual-band edge in mixed phase TNTs as well as the observed variation in Raman and XPS spectra with annealing temperature. Finally, an improved photocatalytic degradation of methylene blue aqueous solution is demonstrated in the presence of a mixed phase and explained in the framework of an efficient transfer of photogenerated electrons from the conduction band (CB) of R to the CB of A and holes from the VB of A to the VB of R across the phase junction in tube walls.

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpcc.0c11081.

  • Indexed XRD spectra of 500 and 900 °C annealed TNTs are shown, while the comparison of experimentally and theoretically obtained lattice parameters of TiO2 is shown. Cross-sectional SEM image of as-grown TNTs is shown, where the primitive cells of A-TiO2 and R-TiO2 are presented. Calculated vibrational frequency and oscillation strength of irreducible modes of A- and R-TiO2 are presented. The vibrational mode vectors of A- and R-TiO2 are exhibited. Moreover, the respective electronic band structures and pDOS are shown. pDOS plots of the VB regions, whereas the XPS results of TNTs annealed at different temperatures are documented. Extracted peak positions from the recorded XAS spectra near Ti L-edge and O K-edge for all annealed samples are presented. Finally, the extracted band structure is schematically shown (PDF)

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Cited By


This article is cited by 3 publications.

  1. Xiaotong Jin, Tianqi Zhang, Kangkang Yuan, Xingxiang Ji, Wenjia Han, Chengshun Li, Zhongjian Tian, Xinqiang Wang. Unveiling temperature-modified electrospun TiO2 nanofibers with size-driven microstructure evolution and enhanced photocatalytic effect. Optical Materials 2021, 1 , 111840. https://doi.org/10.1016/j.optmat.2021.111840
  2. S. Pal, S. Bhowmick, S. A. Khan, A. Claverie, D. Kanjilal, A. K. Bakshi, A. Kanjilal. Annealing temperature-driven near-surface crystallization with improved luminescence in self‐patterned alumina films. Journal of Materials Science: Materials in Electronics 2021, 32 (9) , 11709-11718. https://doi.org/10.1007/s10854-021-05790-0
  3. S. Bhowmick, S. Pal, A. Singh, S. A. Khan, D. R. Mishra, R. J. Choudhary, D. M. Phase, T. K. Chini, A. K. Bakshi, Aloke Kanjilal. Carbon doping-induced defect centers in anodized alumina with enhanced optically stimulated luminescence. Journal of Materials Science: Materials in Electronics 2021, 32 (8) , 10635-10643. https://doi.org/10.1007/s10854-021-05719-7