MBenes: A two-dimensional platform for high-temperature superconductivity via hydrogenation-induced Van Hove singularities

Hydrogenated two-dimensional (2D) materials have recently attracted significant attention for their potential to achieve high-temperature superconductivity via the conventional electron-phonon coupling. However, insufficient surface coordination often limits effective hydrogenation in traditional 2D systems. Here, we identify hexagonal MBenes as an ideal platform with the compact atomic stacking for constructing robust hydrogen-based networks. MBenes are boron-based analogs of MXenes, in which boron (B) atoms form the intermediate layer and transition metals (M) make up the outer layers. A comprehensive study of 53 MBene compounds, including pristine MB, monohydride MBH, and dihydride MBH₂ phases, identifies 29 dynamically and mechanically stable structures. Hydrogen adsorption significantly enhances the superconducting critical temperature (T_c) in Sc-, Ti-, V-, Nb-, and Ta-based MBenes. Among them, VBH₂ exhibits a record T_c of 83 K for hydrogenated 2D superconductors. This enhancement is attributed to a Van Hove singularity (VHS) near the Fermi level, induced by strong hybridization between H s and M d orbitals. Biaxial strain calculations further confirm the decisive role of the VHS by showing a suppression of T_c when the VHS shifts away from the Fermi level. Furthermore, except for TaBH₂, MBH₂ (M = Sc, Ti, V, Nb) exhibit three-gap superconductivity, with anisotropy stemming from the dispersive nature of M d orbitals. This research constructs a robust theoretical basis to probe high-temperature superconductivity and its fundamental origin in hydrogenated MBenes.