First-Principles Calculations of TiB MBene Monolayers for Hydrogen Evolution

In recent years, the sustained growth of attention on MXenes and their derivatives (such as MBenes) encourages this 2D material to be a rising star, thereby attracting more researchers’ interests on their properties. The recent advance has shown that a layered MBene, TiB, has been successfully synthesized in experiment. This newly discovered 2D material adds to a very recent member of the MBene materials family, however, there are few reports revealing its properties and applications. In this account, we utilize first-principles techniques to investigate this newly discovered MBene toward its mechanical and electronic properties as well as its catalytic activity for hydrogen evolution reaction (HER). The results show that TiB monolayer is electronically metallic and possesses excellent mechanical and dynamical stability. Particularly, the slight presence of surface 2DEG-FS (two-dimensional electron gas in free space) state indicates that TiB monolayer could be potentially used in electronic devices for a low-barrier electron transport channel. Additionally, for the catalytic applications, the TiB monolayer with O-termination (TiB-O*) demonstrates thermoneutral Gibbs free energy of atomic hydrogen adsorption (ΔGH*°, about 0.03 eV), approaching the ideal value of 0 eV and suggesting that it can be a promising 2D electrocatalyst to promote HER. The thermodynamic HER activity of TiB–O* is higher than those of most carbide-based MXenes. Our predictions on this newly synthesized MBene material reveal it would hold great promise in electronic and electrocatalytic applications.