PREPARATION OF WS2/TIO2 NANOSTRUCTURES FOR PHOTOCATALYTIC APPLICATIONS

Abstract

The energy from fossil fuels has been recognized as a main factor of global warming and environmental pollution. Therefore, there is an urgent need to replace fossil fuels with clean, cost-effective, long-lasting, and environmentally friendly fuel to solve the future energy crisis and the environmental issues. One of the promising routes is the semiconductor-based solar driven photocatalysis, which is believed to address several critical issues such as the production of sustainable chemical fuel, and the degradation of toxic pollutant dyes. Among various materials, oxide semiconductors, and especially TiO2 have been extensively studied and used as a photocatalyst, owing to its advantages such as low cost, nontoxicity, and chemical stability. However, the application of TiO2 as a photocatalyst is limited by some shortcomings such as high rate of electron-hole recombination and the relatively wide band gap that prevents the absorption of visible light. Therefore, some strategies are required to overcome these limitations. Various techniques and strategies have been constructed to overcome the drawbacks of TiO2 material such as nanostructured morphology and the construction of heterostructures. In this work, the photocatalytic performance of TiO2 was enhanced through two main routes. The first route is providing a controllable growth over the hydrothermally grown TiO2 nanorods. In this regard, the effect of KBr salt on the growth of TiO2 nanorods (NRs) was systematically studied. The results revealed that the presence of KBr molecules affects the growth rate by suppressing the growth in the lateral direction and allowing for axial growth. This results in affecting the morphology by decreasing the diameter of the nanorods, and increasing the free space between them. Enhancing the free spaces between the adjacent nanorods gives rise to a remarkable increase in the internal surface area, with more exposure side surface. The second route of enhancing the TiO2 photocatalytic activity is the construction of heterostructure. To get benefit from the enlargement in the inner surface area of the hydrothermally grown TiO2 NRs, WS2 nanoflakes / TiO2 nanorods heterostructure was obtained by optimizing the height between the precursor and the substrate, which provides a control over the size of the flakes. In addition, the achieved WS2/TiO2 heterostructures were evaluated as photocatalysts for Rhodamine B degradation, and photoelectrochemical activity (PEC).