Photo-Physical Studies and Bandgap Engineering on Transition Metal Chalcogenides for Applications in Photocatalysis

Abstract

Two-dimensional (2D) transition metal chalcogenides (TMCs) based photocatalysts have recently attracted significant research attention for addressing the current worldwide challenges of energy shortage and environmental pollution. This thesis is mainly focused on the design and development of visible-light-driven TMCs based photocatalytic systems that are useful for both the generation of clean energy through solar water-splitting reaction and also towards the degradation of harmful organic pollutants present in water. The influence of structure-to-photocatalytic property relationship (size and shape effects) of semiconductor nanostructures are determined by systematic modifications in the synthesis methods to obtain photocatalysts of different size and morphology and their role in enhancement of the photocatalytic activity is studied. Significant attention is paid on building heterojunctions between two semiconductors having well-aligned band structures and possessing intimately contacted interfaces that are propitious to the effective separation and transfer of photogenerated charge carriers, bringing an excellent performance. Furthermore, firstprinciples calculation based on density functional theory (DFT) are used to investigate the structural, electronic (band structure and density of states) and optical properties of the TMCs-based photocatalysts. Besides, band edge positions of the semiconductor and the band alignment with respect to the normal hydrogen electrode is determined theoretically. It is anticipated that this work will provide a better understanding of the fundamental photocatalytic mechanism, assisted by the development of advanced photocatalysts and studying their photocatalytic performance towards both environmental remediation and production of clean energy.