5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Preparation Of Narrower 1-d Nanostructured Tungsten Oxide Thin Film By Precursor Feed Rate Control

The hydrogen is one of the most promising renewable energy sources. The hydrogen production methods are various such as steam reforming, plasma reforming, and electrolysis. The photoelectrochemical (PEC) water splitting can be produced the hydrogen from the unlimited source that is water and solar light energy, it is attractive method. The photocatalyst in PEC water splitting creates the electron-hole pair, it split the water to hydrogen and water by redox reaction [1]. The tungsten oxide is photocatalyst material which has band gap of 2.8 eV, suitable electrical property and good stability in water and under the sunlight [2-4]. The nanostructure is one of the important factors to decide the PEC performance of photocatalyst. Photo-generated electron and hole in photocatalyst can be recombined during transport to active site, therefore their required transport distance needs to be reduced. Thus narrower 1-D nanostructure can be reduced the recombination of electron and hole, it leads enhancement photocatalytic activity [5]. furthermore, if the growth of nanostructured photocatalyst can be controlled to 1-D nanostructure, improvement of PEC water splitting performance can be expected due to maximizing both light absorption and charge collection [6]. Flame vapor deposition (FVD) is a synthesis method for preparation of thin films. The high purity and crystallinity 1-D nanostructured tungsten oxide thin films also can be synthesized rapidly and economically by FVD method [5-7]. The nanostructure of synthesized thin films are transformed by control of process parameters, therefore the research about the effect of process parameters are very important. effective synthesis of 1-D nanostructured thin film will be possible only through it. In this study, tungsten oxide thin films were synthesized by FVD method using the lab-made flame reactor. This reactor is included precursor feeding machine, it can control precursor feed rate freely and uniformly. But the conductive layer of the substrate was damaged when the initial precursor feed rate was too low [7]. The higher initial precursor feed rate was compelled, but it was lead to increase the diameter of nanostructures [7]. We suggest the method that reduces the precursor concentration during deposition to solve this problem. The total deposition time was fixed, and the initial precursor feed rate was same but the feed rate was reduced during the deposition for getting the narrower 1-D nanostructure. The prepared films were confirmed their nanostructures through UHR-SEM (Ultra High Resolution Scanning Electron Microscope) measurement (Figure 1). Similar 1-D nanostructured tungsten oxide thin films (nanotube structure) were confirmed but their diameters of nanotube were shown the difference. Their diameters ware reduced depend on feed rate decrease. In conclusion, This method in FVD process can be the technique for the preparation of narrower 1-D nanostructured tungsten oxide thin film.
Sang-Hyeok Yoon, Kyo-Seon Kim