Solid-Solution MXenes and Their Properties

MXenes are relatively new additions to the two-dimensional (2D) materials category and have become the fastest-growing family among them. Coexistent to their unique and uncommon properties, such as high electrical conductivity, excellent hydrophilicity, and tailoring of surface functional groups, MXenes have found potential applications in a variety of fields, such as energy storage and conversion, electromagnetic interference shielding, sensors, biomedical devices, catalysis, and so on. The chemical formula of MXene is M n +1X n T x (M = transition metals, X = carbon and/or nitrogen, T x = surface terminated functional groups, and n = 1-4). In the solid solution MXenes, more than one element in M and X sites are randomly distributed in a single M n +1X n slab without forming any impurity phase. In this chapter, we systematically discussed the structures, compositions, and processing of each group of solid solution MXenes depending on their n value. The wide variety of M elements, carbon and/or nitrogen ratio, the overall compositions, and surface functional groups influence their properties. Significant changes in the electronic transport, optical, plasmonic, photothermal, mechanical, and magnetic properties are addressed with existing challenges. The chapter concludes with an outlook for future expansion of the solid solution MXenes.