Black TiO2 Thin Films Production Using Hollow Cathode Hydrogen Plasma Treatment: Synthesis, Material Characteristics and Photocatalytic Activity

Abstract

Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450 °C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

Black TiO2 Nanotube Array/BiVO4 Heterojunction Photocatalysts for Tetracycline Removal with High Solution Detoxification Efficiency

“…Similar to Ti 2p, a small negative shift in the binding energy of O 1s was also observed for B-TiO 2 compared to W-TiO 2 . Moreover, the percentage of integrated areas of defect-to-lattice peaks (S defect /S lattice ) was increased from 15% for W-TiO 2 to 20% for B-TiO 2 , which confirms the presence of more oxygen vacancies or defects in B-TiO 2 than in its counterpart . For heterojunction samples, the deconvolution of the O 1s curve was also fitted by two peaks, located at 530.4 and 531.3 eV, which were consistent with the reported values for oxygen in BiVO 4 .…”

Differentiating and Understanding the Effects of Bulk and Surface Mo Doping on CO2 Hydrogenation over Pd/Anatase-TiO2

“…Meanwhile, Figure c shows that on samples that mostly have surface Mo species, in the O 1s region, the 531.3 eV component, which is associated with O in reduced environments, − is more prominent (∼10% compared to 6%, values in Table S3), indicating higher reducibility of the support surface. Since the reduction level of Ti is not altered by Mo (XP spectra in the Ti 2p region shown asFigure S8), the enhanced reducibility is caused by the high reduction level of surface Mo x O y clusters.…”

Large Effect of Temperature Cycling on the Electrical and Optical Properties of TiO2:H Thin Films

“…The intrinsic defects and respective Ti 3+ and O – polarons are known to introduce localized band gap states. ,,− Additionally to the increase in the electrical conductivity, this results in a red shift of the optical absorption onset. In hydrogenated titania, in which not only extrinsic hydrogen dopants but also intrinsic defects exist, the optical absorption of visible light changes the material’s appearance into either a blue, − gray/black, − or under certain conditions even a red color …”

“…They also reported a huge valence band tail of roughly 2.2 eV in their amorphous shell/crystalline core structure, thus achieving an optical absorption onset already at 1.0 eV. Many followed this amorphous shell/crystalline core structure concept in their studies, but only a few studied homogeneously hydrogenated titania in the form of thin films. ,, …”