MBenes: progress, challenges and future

The prevalence of MXenes, two-dimensional (2D) transition metal carbides/nitrides separated from layered MAX phases, has generated much interest in exploring 2D transition metal borides during the past decade. In 2017, we first reported a new family of 2D transition metal borides as analogues to MXenes and coined a catchy name for them, MBenes. Over the last five years, MBenes have gained more and more attentions in the fields of nanomaterials, physics and chemistry. The promising future of MBenes is foreseeable since they have exhibited many intriguing properties and been widely studied for energy storage and electrocatalysis applications. However, research on MBenes is still in its infancy, with many expected properties and applications awaiting to be explored. In this review, first we made a scientific classification of 2D transition metal borides and proposed an explicit definition of MBenes: a family of 2D transition metal borides with sandwich-like structures which are derived from layered MAB phases. Then we reviewed the progress of synthesis methods, properties and applications of MBenes for energy storage and electrocatalysis. Finally, the discussions on the existing problems in experimental synthesis and theoretical calculations along with the perspectives and prospects of MBenes were presented.