Fabrication of Photocatalytic Thin Film by Vacuum Kinetic Spray Method

Abstract

Vacuum kinetic spray method is a dry particle deposition method, also known as the nano-particle deposition system (NPDS), to deposit metals and ceramics onto different substrates at room temperature without using any toxic chemicals. Nowadays, photocatalysis has been using as a green and clean process for renewable energy and environmental remediation. Various semiconductor materials like TiO2, WO3, Fe2O3 and so on are utilized in the photocatalysis field. Individual semiconductor materials can show poor photocatalytic efficiency because of high recombination effect of electron and holes. Therefore, no individual semiconductor can meet the required goal of photocatalysis. Consequently, the design of visible-light-driven semiconductor photocatalysts is a very important issue in terms of harvesting photon energy in the visible range. Recently, graphene has gained an enormous research interest due to its high specific surface area and electron mobility. In this study, NPDS is utilized to make WO3 and its composite with (0-30) wt.% graphite thin films on polypropylene substrate. To evaluate the photocatalytic activity of the fabricated thin films, degradation of methylene blue dye under illumination of light for 2 hours was observed. Degradation of the methylene blue dye was evaluated using absorbance values measured by UV/Vis spectroscopy at the wavelength of 665 nm. The results showed that the photocatalytic performance was significantly enhanced the graphite content is increased with WO3. The highest activity was observed for 15 wt.% graphite with WO3 thin films. The photocatalytic reaction followed pseudo-first-order kinetics. The kinetic rate constant for graphene/WO3 with 15% graphite is 1.5 times higher than that of pristine WO3 film. Repeatability determines the feasibility of thin films in using real applications. Here, all the thin films showed good stability up to five cycles. The deposited thin films were observed using field effect scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectroscopy. FE-SEM shows that micro-sized graphite/WO3 particles are cracked into small pieces during deposition due to the high impact velocity by NPDS. X-ray diffraction showed the absence of any graphite peak in the composite thin film. Finally, the existence of graphene in the fabricated thin film was confirmed by Raman spectroscopy. Finally, it is suggested that NPDS can be a suitable process for photocatalytic thin film fabrication at room temperature. The prepared thin films can be easily used for the photocatalytic applications.