Structure Design and Performance Research of WO₃ Hydrogen Gasochromic Film Prepared by Solvothermal Synthesis Assisted with Electrodeposition of Seed Layer

Abstract

air is a kind of hydrogen-sensitive material and can change its color when exposed to hydrogen. This hydrogen gasochromic phenomenon provides a visualized and safer method without electrical signals to detect hydrogen.As a versatile material, WO 3 film can be directly used for photocatalysis and electrochromism without catalyst. Researchers have done a lot of work in these fields. [1,2] However, catalyst loading is essential to observe hydrogen gasochromism of WO 3 film at room temperature. Currently, although many issues regarding the mechanism of WO 3 hydrogen gasochromism have not been fully understood, the processes of adsorption and decomposition of H 2 or O 2 on the surface of the catalyst and the diffusion of H or O atoms between catalyst and WO 3 are widely recognized in different models. The commonly used catalyst materials are Pt and Pd. [3,4] Meanwhile, some researchers also use PdO, PtO x or Pd-Pt alloy as catalysts. [5,6] Usually, there are two ways to load catalyst. One is to prepare WO 3 film first, then load the catalyst on it. [4,6,7] The other is to merge the preparation of WO 3 film and the loading of catalyst into one step. [8,9] Many methods have been used to prepare WO 3 films, such as PVD, [10][11][12] CVD, [13,14] sol-gel method, [15,16] hydrothermal/ solvothermal method, [17][18][19][20] electrodeposition and anodic oxidation. [21][22][23][24] The hydrothermal/solvothermal method can be used to prepare nanostructured film with simple experimental conditions and low cost. Compared with dense film, nanostructured porous film with the high specific surface area often has better catalysis and reaction performance, so the hydrothermal/ solvothermal method is a promising method to prepare nanostructured porous WO 3 film. Before hydrothermal/solvothermal synthesis, many researchers prepare seed layer on the substrate firstly for the consideration of the provision of nucleation sites and good adhesion between substrate and film. A typical process of preparing seed layer includes synthesis of WO 3 sol, spin coating, and annealing. To guarantee the quality of the seed layer, this process has to be repeated several times. As a result, the time-consuming and laborious heat treatment is indispensable for preparing seed layer in the solvothermal synthesis of The time-consuming and laborious heat treatment is indispensable for preparing seed layer in solvothermal synthesis of WO 3 film. Herein, WO 3 film is prepared composed of single crystal WO 3 nanowires on indium tin oxide (ITO) glass assisted with simple and energy-saving electrodeposited seed layer for the first time. The catalyst Pt is sputtered on it for 30 s after WO 3 film is synthesized to form the hydrogen gasochromic film. The film structure is redesigned to improve its hydrogen gasochromic properties further. Before WO 3 film is solvothermally synthesized, Pt is sputtered on seed layer for 15 s, then it is sputtered for 15 s again after WO 3 film is prepared. The Pt sputtered on seed layer greatly changes the morphology of nanowires, makin...

Characterization and Modeling of WO3 Nanowires Synthesized via the Solvothermal Method: A Proposed 8-Pointed Star Prism Structure

“…Compared with the PDF card, the (002) peak of the WO 3 phase is significantly enhanced, indicating the selective orientation of (002). The result of XRD is consistent with our previous study …”

“…It should be noted that strictly speaking, the product of the solvothermal process is W 18 O 49 (JCPDS 71-2450), and it has been investigated in our previous work. 5 After annealing at 400 °C for 1 h, W 18…”

“…The result of XRD is consistent with our previous study. 5 Subsequently, SEM images were taken to investigate the morphology of the WO 3 film, as shown in Figure 2. It can be seen that the WO 3 film is composed of nanowires that are 40−50 nm in diameter and 400 nm to 1 μm in length.…”

“…WO 3 is a multifunctional material that can be used for hydrocracking catalysts, photocatalysis, electrochromism, gasochromism, etc. − It is also an important material for the industrial synthesis of the scheelite phase such as Ag 2 WO 4 , SrWO 4 , CaWO 4 , etc. − Currently, many methods have been used to prepare the WO 3 film, such as PVD, − CVD, , sol–gel, , hydrothermal/solvothermal, , electrodeposition, anodic oxidation, , and molten salt synthesis. , Among these methods, the solvothermal method is paid much attention because of its low cost and simple experimental conditions. , It has been confirmed that solvothermally synthesized WO 3 films are composed of basic units such as nanowires, nanorods, nanoplates, nanosheets, and so on. Further research indicates that each of the aforementioned basic units is a WO 3 single crystal with a specific growth direction, and the growth direction is varied in different studies, indicating that it is affected by many parameters of the solvothermal process. − As is known to all, besides the growth direction, the shape of a single crystal is also affected by the exposed lattice planes.…”

Rainbow‐Colored Carbon Nanotubes via Rational Surface Engineering for Smart Visualized Sensors

“…As is well known, gasochromic materials or sensors can make invisible hydrogen gas visible to the naked eye without electricity or complex equipment. [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ] Thus, endowing CNTs with stimuli‐responsive chromatic properties may allow these materials to be used in promising applications, such as on CNT‐reinforced hydrogen tanks to provide a visual warning of hydrogen leaks and prevent fires and explosions.…”