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An Investigation on Physical and Photochemical Properties of Sol-Gel Derived MWCNT-WO3 Nanocomposite thin Films

Yousefzadeh, Samira | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40987 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Moshfegh, Alireza
  7. Abstract:
  8. WO3 have good electrochromic, gas sensor, photocatalyst, phoelectrochemical (PEC) properties. due its properties, tungsten oxide have many application in technology and industry. In this thesis, pure WO3 thin film and MWCNT-WO3 nanocomposite thin films with different weight percent of MWCNT/WO3 utilize for energy domain, particular hydrogen production with phoelectrochemical reactions spiliting water. For this purpose, initially WO3 thin films were deposited on glass and ITO substrates using sol-gel dip-coating method. Optical and surface properties of the films dried at 100ºC and annealed at 400 ºC had been investigated. UV-Visible spectrophotometer, atomic force microscopy (AFM), X-ray diffraction, Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) have been employed. According to our data analysis, the band gap and the transmittance of the films decreased by increasing annealing temperature but the average grain size the films and their surface roughness increased by increasing the annealing temperature. Moreover, MWCNT-WO3 nanocomposite thin films were deposited on both glass and ITO substrates using sol-gel dip-coating method. For better MWCNT dispersion and obtaining a homogeneous sol and creation of reaction group on surface of MWCNT, its powder with chemical method using nitric acid(HNO3) and hydrochloric acid (HCl) refluxed.Then the suspension was filtered, washed with deionized water and dried at room temperature, different weight percent of MWCNT including of 0.5, 1, 2, 5 and 10wt% were used for the synthesis of composite sample. As for optical analysis, the band gap energy of the films didn’t change significantly. The XPS analysis confirmed presence of oxygen functional group rising from reflux process and reaction between WO3 and MWCNT. Moreover, WO3 thin films containing different weight percent of MWCNT photo electro chemical properties studied in details. Based on photo electro chemical data analysis, the highest value of photocurrent achieved for the MWCNT(1wt%)-WO3 thin film. The addition of MWCNT to the caused increasing photocurrent density WO3. It is important to know that MWCNTs are eminent electronic conductors that can transfer electron from WO3 and reduce electronic accumulation on WO3 and so prevent recombination of electron/hole pairs
  9. Keywords:
  10. Sol-Gel Method ; Photoelectrochemical Cell ; WO3 ; Multi-Walled Carbon Nanotube ; Nanocomposite

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