Two-dimensional (2-D) materials are low dimensional nanostructured materials with extraordinary optical, electronic, and mechanical properties that show significant potential for optoelectronic, electronic, and photonic applications. The exceptional properties of the 2-D materials emerge due to quantum confinement, where layered bulk counterpart materials are thinned to few-layered sheets.

One of the most attractive examples of a 2-D material is graphene, which is extracted from graphite, it is an interesting 2-D material owing to its characteristic properties such as extremely-high charge carrier mobilities, high mechanical strength, etc.^1,2  The charge carrier mobility is one of the most important parameters of a 2-D material or any other material that decides how a fast charge carrier such as an electron and hole can move within a material under applied electric field. The applicability of synthesized 2-D material in various electronic devices is determined by carrier mobility.³  Following the development and achievements of graphene in recent years, a wide range of 2-D materials such as transition metal dichalcogenides (TMDCs), transition metal halides (TMHs), transition metal oxides (TMOs), silicene, phosphorene, black phosphorus, metal nitrides and carbides (M-Xenes), etc., seek the world-wide attention of scientists and researchers. 2-D layered materials exhibit a variety of significant phenomena in a wide-band insulator, narrow-bandgap semiconductor, semimetal, or metal, as well as unique electrical and optical properties that provide a new direction for a variety of applications such as energy storage, sensors, LEDs, and photocatalysis (see Figure 2.1). Specifically, 2-D materials have attracted tremendous interest as an important class of photocatalysts owing to their properties which including large specific surface area, enhanced charge carrier separation, rich surface-active sites, which are quite distinctively different features to their bulk counterparts. The following properties distinguish the 2-D materials from their bulk counterparts.