Discovery of Two‐dimensional Hexagonal MBene HfBO and Exploration on its Potential for Lithium‐Ion Storage

Abstract The practical applications of two‐dimensional (2D) transition‐metal borides (MBenes) have been severely hindered by the lack of accessible MBenes because of the difficulties in the selective etching of traditional ternary MAB phases with orthorhombic symmetry ( ort ‐MAB). Here, we discover a family of ternary hexagonal MAB ( h ‐MAB) phases and 2D hexagonal MBenes ( h ‐MBenes) by ab initio predictions and experiments. Calculations suggest that the ternary h ‐MAB phases are more suitable precursors for MBenes than the ort ‐MAB phases. Based on the prediction, we report the experimental synthesis of h ‐MBene HfBO by selective removal of In from h ‐MAB Hf 2 InB 2 . The synthesized 2D HfBO delivered a specific capacity of 420 mAh g −1 as an anode material in lithium‐ion batteries, demonstrating the potential for energy‐storage applications. The discovery of this h ‐MBene HfBO added a new member to the growing family of 2D materials and provided opportunities for a wide range of novel applications.