Synthesis of Microwave Assisted Transition Metal Dichalcogenides for the Catalytic Degradation of Organic Pollutants

Abstract

Chapter 1: A brief introduction about hazardous pollutants and wastewater treatment methods is given with a precise discussion on advanced oxidation processes including semiconductor photocatalysis. This section also illustrates the photocatalytic mechanism in detail using semiconductors. Furthermore, an extensive discussion on transition metal dichalcogenides (TMDCs) is provided with description of their unique photo or electrocatalytic properties like high surface-to-volume ratio, excellent charge transfer capacity, mechanical strength, and low bandgap energy. The chapter also highlights the advantages of microwave-assisted methods for synthesis of different TMDC composites and the requirement for the formation of heterojunction composites to overcome charge recombination. In addition, the research gaps, research objectives, and characterization approaches have been combined with specifications. Chapter 2: The photodegradation of toxic pollutants is a promising way to deal with water-pollution. In this regard, MoS2/g-C3N4 (MSC) composites with varying weight-ratios were prepared via fast one step microwave-assisted method. The material was characterized by XRD, XPS, EDS, FESEM and HRTEM which validate the successful formation of catalyst having the flower-like and sheet-like morphologies of MoS2 and g-C3N4, respectively. The PL and UV-vis DRS spectra exhibit low recombination-rate and band-gap (1.7 eV) which is appropriate for efficacious visible-light degradation. The photocatalytic performance of catalysts was then analyzed by the degradation of a model dye methylene blue and pesticide fipronil. Best results were obtained by 5:1 MSC (98.7% degradation efficacy; rate constant 0.0261 min-1) in 80 min under sunlight. The effects of solution pH, catalyst-dose, scavengers and illumination-area were also explored. The catalyst is highly-reusable as confirmed by the characterization and degradation studies (~82% efficiency) after 5-cycles.