CONSTRUCTION OF FE2O3/TRANSITION METAL DICHALCOGENIDES HETEROSTRUCTURES FOR DYES PHOTODEGRADATION

Abstract

Photocatalysis has been widely implemented in water purification due to its sustainability, high efficiency in degrading pollutants with low energy consumption, and it is economically and environmentally friendly. Hematite, also known as α-Fe2O3, is a promising photocatalyst due to its outstanding stability compared to other states of Fe2O3, non-toxicity, low cost, excellent antiferromagnetic properties, abundance in nature, corrosion resistance in acidic and alkaline media, recyclability, and the ability to harvest up to 40% of the solar spectrum. On the other hand, α-Fe2O3 shows several limitations including high electron-hole recombination rates, low conductivity, and small hole diffusion length. Forming heterostructures with Transition metal dichalcogenides (TMDs) helps in enhancing the performance of Fe2O3 by reducing the recombination rate and altering the transport rout. In the past few decades, a plenty of research work was done on hematite to enhance its photocatalytic activity against water pollutants through several strategies including morphology control, doping and heterojunction formation. Indeed, constructing semiconductor heterojunctions has been considered to be one of the most effective methods as it provides the distinct properties of the combined elements and overcomes the limitations of each component. However, research work achieved on combining hematite with TMDs is still narrow. Thus, this study aims to accomplish an enhancement in the photocatalytic performance of Fe2O3 by constructing a heterostructure with a TMD material (WS2). To the best of our knowledge, this is the first research work to prepare hematite nanorods heterostructured with a TMD material synthesized via chemical vapor deposition (CVD) method. Furthermore, this hybrid system is optimized in this research in order to achieve an improved photodegradation activity against synthetic dyes such as Methylene Blue. In this thesis, two reaction conditions of hematite synthesis were studied, which are precursors' ratio and annealing temperature, and they were found to affect the morphology of the hematite nanorods. Also, the distance between the tungsten source and the α-Fe2O3 sample (height) was found to influence the growth of WS2 and the evolved photocatalytic activity of the obtained heterostructure which was examined against Methylene Blue dye solution under solar simulator irradiation. The best photodegradation performance was obtained by the heterostructure synthesized at a height of 6 mm with a degradation percentage of 64.9%, that is 3.4 and 2.8 times better than bare Fe2O3 and WS2, respectively.