Research Projects

Two-dimensional (2D) layered materials possess unique properties which do not exist in their bulk counterparts. In parallel, heterostructures (van der Waals heterostructures) realized by vertically stacking different 2D materials throw up further exotic properties such as interlayer excitons, unconventional superconductivity and so on. Though these 2D superlattices are inherently competent in bringing new chemistry such as charge transfer, redox chemistry, and chemically active sites, their study is mostly limited to understanding the fundamental emerging physics. High difficulty in obtaining a reasonable quantity of these artificial materials and complex process integration make their applicability limited in the chemistry world. Here, I propose a new class of 2D superlattices, i.e., misfit layered compounds (MLCs), which are seamlessly grown as artificial heterostructures and can be easily scaled up to exploit their applications in energy storage and conversion. MLCs are intercalation compounds with an incommensurate layered structure consisting of alternating building blocks MX and TX2 (MX is monochalcogenide with rocksalt structure and TX2 is dichalcogenide with hexagonal structure). MLC geometry has an additional advantage over normal 2D materials, where we can precisely control one of the components without affecting the other. Over the last few years, we have demonstrated the growth and characterization nanotustructures of several MLC from LnS-TaS2 (Ln= rare earth). Significant efforts have been devoted to understanding their atomic structure, charge transfer properties, and thermodynamic and kinetic stability limits of the nanostructures. Though these materials promise to be a good redox host and offer superior electrical conductivity with stable rigid and soft superlattice, their electrochemical energy conversion and storage properties have not been explored except for two recent studies on PbNbS and PbSnS systems. Here, I propose to explore the electrochemical energy storage properties of the chalcogenide-based MLCs family, particularly LnS-MS2 (Ln= Ce, La, Sm Gd; M= Ta, Ti) system. The properties of these MLCs can be tailored from semiconductor to semi-metallic range by carefully choosing the binary units. We will establish an experimental protocol to grow 2D flakes and 1D nanotubes of various LnS-TaS2 MLCs via chemical vapor transport techniques. The materials will be thoroughly characterized for their atomic structure, composition and charge transfer properties. We will investigate the Li/Na storage properties of these materials by fabricating the half-cell against the Li/Na. The outcome of this project will bring these new directions MLCs and their applications in Energy sector. It will enable us to understand how soft lattices interact with lithium, providing capacity and preventing structural decomposition. At the same time, the rigid sublayers maintain structural integrity and facilitate electron and ion transport.