Study Of Low Dimensional Tungsten Oxide By Anodization And Sol-Gel Methods
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Date
2018-06
Authors
Chai, Yingqi
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Low dimensional tungsten oxides (WO≤3) have attracted considerable research attention due to potential applications such as electrochromic devices, gas sensors, photocatalysts for water splitting, dye-sensitized solar cells and humidity sensors. The use of tungsten oxide for surface-sensitive device applications requires cost-effective fabrication of tungsten oxide with controllable morphological property. Both anodization and sol-gel methods offer facile ways to synthesize nanostructured tungsten trioxide (WO3). However, inadequate works have been done to employ anodization and sol-gel techniques for the fabrication of nanostructured WO3. In this thesis, investigations of the use of anodization and sol-gel methods for the formation of nanostructured WO3 are presented. The effects of anodization parameters (electrolyte, voltage, duration, and temperature) and sol-gel parameters (acid volume, ageing duration, and mixing rate) on the properties of the WO3 as well as their photoelectrochemical and humidity sensing properties were also examined respectively. Anodization in different electrolytes resulted in different nanostructures. Nanoporous layer of ~400 nm could be formed in oxalic acid while nanoplates layer of >1 μm were demonstrated by anodization in HCl and H2SO4. From our experimental results, growth mechanisms of nanopores and nanoplates were both proposed. Photocurrent measurements revealed that nanoporous structure had better photoelectrochemical response as compared to the nanoplate structure. For the fabrication of WO3 by sol-gel method, nanoplates could be formed. Higher
volume of acid, shorter ageing duration and slower mixing rate were found to decrease the size of nanoplates.
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Keywords
Low dimensional tungsten oxide , anodization and sol-gel methods