2D-Transition Metal Borides (MBenes): a comprehensive review of the materials, chemistry, advances, and novel applications

MBenes and MAB phases are emerging classes of materials with unique properties and potential applications. MAB phases, first introduced in 2017, are ternary compounds with a layered structure similar to MAX phases but with boron replacing carbon. These materials have attracted significant attention due to their outstanding mechanical, electrical, and structural properties. MBene phases, derived from MAB phases through selective etching, are 2D materials analogous to MXenes, exhibiting high conductivity, chemical stability, and a broad range of applications. This review provides an in-depth analysis of MBene and MAB phases, including their structures, properties, synthesis methods, and applications. The history of MAB phase discovery and its evolution into MBene phases is discussed, along with advancements in synthesis techniques and the challenges associated with their production. The review also covers characterization methods for these materials, highlighting their distinct features. The properties of MBenes and MAB phases are explored, with a focus on their applications in energy storage, including supercapacitors and batteries, and their catalytic performance in reactions such as the Hydrogen Evolution Reaction (HER), Nitrogen Reduction Reaction (NRR), Carbon Dioxide Reduction Reaction (CO2RR), Oxygen Reduction Reaction (ORR), Nitric Oxide Reduction Reaction (NORR), and Carbon Capture and Storage (CCS). Additionally, their potential in biological and photocatalytic applications is discussed. Lastly, this review addresses the challenges associated with the synthesis and utilization of MBenes and MAB phases. By providing a comprehensive overview from their discovery to their current applications and limitations, this article aims to serve as a foundational resource for researchers and practitioners in the field.