Two-dimensional metal carbides and nitrides from head to toe with energy applications: A topical review

An increase in population and demand for energy are the major challenges in today's world. As the Internet of Things (IoTs) grows, there is a pressing need for new kinds of novel materials. These issues greatly attract the scientific community. Therefore, the hottest topic now is energy conversion and energy storage by using twodimensional (2D) materials beyond that of graphene. In the year 2011, Gogosti et al., and his research team discovered 2D transition metal carbides, nitrides and carbonitrides called MXenes Ti3C2Tx etching from Ti3AlC2 with the help of toxic hydrofluoric acid. Now, so many novel routes have been developed with mild reducing agents, etchants, and intercalants. Many new members of 2D materials have been added to the constellation. MXene based composites have drawn extensive attention from the scientific community owing to their high conductivity and other unique properties such as hydrophilic surfaces, large interlayer spacing, environmental flexibility, large surface area, safety, thermal conductivity, improved electrochemical activity, enhancing faradic capacitance (pseudocapacitance) and reducing the shortcomings in the normal capacitance etc. In this review, we systematically summarize the recent developments and various synthesis mechanisms of different multi-layered material, intercalations, and its different applications as electrocatalysts, Li-ion batteries (LIBs), supercapacitors, biosensors, and other electrochemical storage systems.