Synthesis and applications of double metal MXenes: A review

MXenes are known as a new type of two-dimensional layered materials that are composed of carbide, nitride, or carbonitride of transition metals. In the recent discovery of a new class of MXenes, two transition metals occupy the metal site, called double transition metal MXenes (DTM). These multilayer composites are of interest due to their attractive features such as high ion transport, extensive surface area, and biocompatibility. Some computational methods are used to predict the properties and performance of bimetallic carbonitrides. The most important feature of this category of materials is the stability and amount of formation energy, which directly affects the choice of material in various applications. Density functional theory (DFT) calculations are very beneficial to estimate the thermodynamic stability of DTM MXenes. Of course, proper surface modification with stable terminals is needed to overcome the limitations of DTM MXenes. In this review, the electrochemical, metallic, and magnetic properties of DTM MXene have been presented first. In the following, preparation methods are summarized according to the latest published findings. Then, various applications including hydrogen evolution reactions, anode materials in lithium and sodium batteries, nanomagnetic materials, and special applications have been investigated. Finally, more challenges, prospects, and suggestions for the development of two-dimensional DTM MXenes have been presented.