A comparative study of humidity sensing and photocatalytic applications of pure and nickel (Ni)-doped WO3 thin films

Abstract

Nanocrystalline of pristine and nickel (Ni)-doped tungsten trioxide (WO3) thin films was deposited by chemical bath deposition method. The concentrations of Ni ions were varied from 0 to 10 wt%. In order to improve the crystallinity of the films were annealed at 600 °C for 2 h in the ambient atmosphere. X-ray diffraction results reveal that the WO3 doped with nickel crystallizes in monoclinic structure and the results are in good agreement with the standard JCPDS data (card no: 83-0951). AFM micrographs reveal that average grain size of about 27–39 nm for pure and Ni-doped WO3 thin films. In addition, the band gap of the Ni-doped WO3 nanostructures is facilely tunable by controlling the Ni contents. The humidity sensor setup was fabricated and measured for pure and Ni-doped WO3 thin film sensor with various level of RH (10–90%). The Ni-doped WO3 sensor showed fast response and high sensitivity than pure WO3. The photocatalytic activities of the films were evaluated by degradation of methyl orange, methylene blue and phenol in an aqueous solution under visible light irradiation. The photocatalytic activity of WO3 nanostructures could be remarkably enhanced by doping the Ni impurity.