Influence of water content on structural and electrochromic properties of TiO2 nanotube prepared by anodization

Abstract

TiO2 nanotubes (TNTs) and bamboo-type TNTs structure films were synthesized via anodization from sputtered titanium (Ti) films on indium tin oxide (ITO) glass. Herein, the anodization process was adjusted electrolyte with different amounts of deionized water and ethylene glycol. The optical and structural properties of all films before and after annealing were investigated, which affected electrochromic application. The increasing deionized water content in electrolytes resulted in an increase in the average diameter and a decrease in the average length of TNTs. Furthermore, the bamboo-type TNTs structure was produced at the deionized water volume condition of 3 vol%. The crystallite size of annealed TNTs (a-TNTs) was calculated from the Scherrer equation, which was enhanced when increasing deionized water. TNTs conditions before annealing showed that the amorphous structure and high energy band gap (Eg) exhibited more electrochromic phenomena than the crystal structure. Due to the disordered arrangement of structures, it was easy to insert ions in TNTs. The bamboo-like structure with separate tubes increased the surface area of the reaction, thus exhibiting the best electrochromic properties with ΔT equal to 12.58%.

Tailoring TiO2 Films: The Path to Superior Electrochromic Performance

“…This effect is closely associated with the presence of a larger active specific superficial area and the distinctive morphology inherent to crystalline TiO 2 nanostructures. In this investigation, the observed switching speeds, particularly the bleaching time of 2.10 seconds, were marginally faster compared to values reported in previous studies (Table 1) [11,28,[33][34][35][36][37][38][39][40][41][42][43]. Notably, these switching speeds are better than those documented in earlier literature [11,28,[33][34][35][36][37][38][39][40][41][42][43].…”

“…In this investigation, the observed switching speeds, particularly the bleaching time of 2.10 seconds, were marginally faster compared to values reported in previous studies (Table 1) [11,28,[33][34][35][36][37][38][39][40][41][42][43]. Notably, these switching speeds are better than those documented in earlier literature [11,28,[33][34][35][36][37][38][39][40][41][42][43]. The enhanced switching speed can be ascribed to the island-like morphology illustrated in Figure 5.…”

“…The variation in initiation temperatures for crystallization is directly associated with the specific precursor materials employed [48]. The XRD results of the TiO 2 film developed for EC applications reveal the existence of anatase as well as brookite phases of TiO 2 , each possessing well-established electrochromic properties [38][39][40][41][42][43][44][45]. Despite the presence of these multiple phases, there is a clear inclination in the literature to preferentially utilize the anatase phase of TiO 2 in films designed for EC applications.…”

“…The drawback of the mentioned synthesis lies in its complexity and potential cost implications due to the controlled engineering of defect-rich brookite TiO 2 nanorods, limiting its practical scalability for widespread applications. In 2023, Aiempanakit et al [43] synthesized TiO 2 nanotubes (TNTs) and bamboo-type TNTs structure films by anodizing sputtered titanium (Ti) films on ITO glass, adjusting the anodization process with varying amounts of deionized water and ethylene glycol. The EC performance was influenced by the amorphous structure and high energy band gap (Eg) in TNTs before annealing, with the bamboo-like structure exhibiting the best electrochromic properties, achieving ∆T of 12.58%.…”