Emerging trends in niobium, vanadium, and molybdenum based MXenes applications

MXenes, 2-dimensional (2D) layered materials, have been able to garner immense popularity among researchers and academia alike in recent times. MXenes are typically produced from the selective etching of "A" group metal layer using an etchant (usually HF) from the parent MAX phase structure where M represents a metal from early transition metals. Their unique surface chemistry and intriguing electrochemical behavior, combined with their high biocompatibility, make them ideal as a support matrix for the development of cutting-edge electrochemical energy storage, biomedicine, electrochemical sensing, and biosensing devices. Due to the surging demand for batteries that can enable recent technological advancements such as electric vehicles to reach their full potential, the high specific capacitance and outstanding electrochemical energy storage of MXenes are under extensive research in recent times. Ti-based MXene has shown tremendous potential and thus many excellent reviews appeared around it and other MXenes in general. However, there are not many specialized reviews for other types of MXenes. Herein, we reviewed the current research advances, challenges, and prospects of the three most popular MXenes: Niobium (Nb), Vanadium (V), and Molybdenum (Mo) based MXenes. The applications of each form of MXene have been divided into categories for the reader's convenience. Finally, we have highlighted the challenges and future perspectives.