We demonstrate the electrochromic properties of TiO₂ nanotubes prepared by an anodization process and investigate the effects of heat treatment and viologen incorporation on them. The morphology and crystal structure of anodized TiO₂ nanotubes are investigated by scanning electron microscopy and X-ray diffraction. As-formed TiO₂ nanotubes have straight tubular layers with an amorphous structure. As the annealing temperature increases, the anodized TiO₂ nanotubes are converted to the anatase and rutile phases with some cracks on the tube surface and irregular morphology. Electrochemical results reveal that amorphous TiO₂ nanotubes annealed at 150°C have the largest oxidation/ reduction current, which leads to the best electrochromic performance during the coloring/bleaching process. Viologenanchored TiO₂ nanotubes show superior electrochromic properties compared to pristine TiO₂ nanotubes, which indicates that the incorporation of a viologen can be an effective way to enhance the electrochromic properties of TiO₂ nanotubes.

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• Fabrication of patterned TiO2 nanotube layers utilizing a 3D printer platform and their electrochromic properties
  Kwang-Mo Kang, Seok-Han Lee, Sang-Youn Kim, Yoon-Chae Nah
  Electrochemistry Communications.2024; 169: 107833.     CrossRef

In this study, we demonstrate the photoelectrochromic devices composed of TiO₂ and WO₃ nanostructures prepared by anodization method. The morphology and the crystal structure of anodized TiO₂ nanotubes and WO₃ nanoporous layers are investigated by SEM and XRD. To fabricate a transparent photoelectrode on FTO substrate, a TiO₂ nanotube membrane, which has been detached from Ti substrate, is transferred to FTO substrate and annealed at 450°C for 1 hr. The photoelectrode of TiO₂ nanotube and the counter electrode of WO₃ nanoporous layer are assembled and the inner space is filled with a liquid electrolyte containing 0.5 M LiI and 5 mM I₂ as a redox mediator. The properties of the photoelectrochromic devices is investigated and Pt-WO₃ electrode system shows better electrochromic performance compared toWO₃ electrode.

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• Synthesis and characterization of nitrogen-doped TiO 2 coatings on reduced graphene oxide for enhancing the visible light photocatalytic activity
  Yifan Zhang, Hye Mee Yang, Soo-Jin Park
  Current Applied Physics.2018; 18(2): 163.     CrossRef
• Photocatalytic and Adsorption Properties of WO3 Nanorods Prepared by Hydrothermal Synthesis
  Su-Yeol Yu, Chunghee Nam
  Journal of Korean Powder Metallurgy Institute.2017; 24(6): 483.     CrossRef
• Synthesis and Photo Catalytic Activity of 10 wt%, 20 wt%Li-TiO2 Composite Powders
  Hyeong-Chul Kim, Jae-Kil Han
  Journal of Korean Powder Metallurgy Institute.2016; 23(1): 33.     CrossRef

Anodic aluminum oxide (AAO) has been widely used for the development and fabrication of nano-powder with various morphologies such as particle, wire, rod, and tube. So far, many researchers have reported about shape control and fabrication of AAO films. However, they have reported on the shape control with different diameter and length of anodic aluminum oxide mainly. We present a combined mild-hard (or hard-mild) anodization to prepare shape-controlled AAO films. Two main parameters which are combination mild-hard (or hard-mild) anodization and run-time of voltage control are applied in this work. The voltages of mild and hard anodization are respectively 40 and 80 V. Anodization was conducted on the aluminum sheet in 0.3 mole oxalic acid at 4°C. AAO films with morphologies of varying interpore distance, branch-shaped pore, diameter-modulated pore and long funnel-shaped pore were fabricated. Those shapes will be able to apply to fabricate novel nano-materials with potential application which is especially a support to prevent volume expansion of inserted active materials, such as metal silicon or tin powder, in lithium ion battery. The silicon powder electrode using an AAO as a support shows outstanding cycle performance as 1003 mAh/g up to 200 cycles.

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• Nano silicon encapsulated in modified copper as an anode for high performance lithium ion battery
  Jong-Keun Ha, Anupriya K. Haridas, Gyu-Bong Cho, Hyo-Jun Ahn, Jou-Hyeon Ahn, Kwon-Koo Cho
  Applied Surface Science.2019; 481: 307.     CrossRef