First demonstration of possible two-dimensional MBene CrB derived from MAB phase Cr2AlB2

In this communication, the possibility for the preparation of two-dimensional MBene CrB from MAB phase Cr2AlB2 is demonstrated for the first time. Herein M is a transition metal, A is a group IIIA or IVA element and B is boron; MAB phases are layered transition metal ternary borides, MBene is used to emphasize the loss of A group element from the parent MAB phases and to highlight the 2D nature. The possible 2D CrB nano sheets are prepared by selectively etching out Al layers from Cr2AlB2 by immersing the Cr2AlB2 powders in dilute HCl solution at room temperature. The as-prepared 2D CrB nano sheets are examined using X-ray diffraction and scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). In addition, different structure models are built to explain the observed phenomena. The discovery in this work opens a door to the synthesis of a large number of new 2D MBenes from MAB phases.