Superior mechanical and thermal properties of oxygen terminated trigonal Mo2B2 MBenes

Abstract

The mechanical and thermal properties of transition metal borides (MBenes) have a significant influence on their practical performance for energy applications, yet they remain insufficiently studied. Herein, we employ density functional theory to investigate these properties of Mo₂B₂ MBenes terminated by –F, –O, and –OH groups. The results reveal that the trigonal Mo₂B₂ MBenes exhibit the greatest stability among the four different pristine phases studied (hexagonal, orthorhombic, trigonal, and tetragonal). Their mechanical properties can be most significantly affected by the terminal group. While both –O and –OH can greatly enhance the mechanical strength of MBenes, the termination by –OH can decrease the Pugh ratio to 1.58, indicating the increased brittleness. Additionally, introducing the –OH terminal group has the highest impact on their thermal properties, as evidenced by a remarkable 333% rise in the thermal expansion coefficient. Our findings, therefore, predict that the oxygen-terminated trigonal Mo₂B₂ MBene can be a better candidate for energy conversion and storage applications in terms of its superior mechanical and thermal properties.