Effective treatment of hydrogen boride sheets for long-term stabilization

Abstract

Two-dimensional hydrogen boride (HB) sheets prepared via the ion-exchange reaction from magnesium diboride (MgB₂) are known to possess several intriguing properties for a wide range of applications; however, previous reports have shown that the sheets prepared using this method contain small amounts of reactive components, making them unsuitable for certain applications. Therefore, developing a method for preparing HB sheets that exhibit long-term stability and do not contain reactive species is essential. In this study, we developed an effective treatment method for achieving long-term stabilization of HB sheets. We found that by pre-treating the HB sheets with water and then filtering the dried product from an acetonitrile dispersion, we could achieve excellent long-term stability over nine months. This stability was maintained even outside of a glovebox, with no H₂ released by the decomposition and/or reaction. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) absorption spectroscopy measurements revealed that the sample exhibited pure HB characteristics with negatively charged boron and B–H–B and terminal B–H bonds, even after nine months of storage. Furthermore, based on thermal desorption spectroscopy (TDS) measurements, the presence of reactive species in the as-prepared HB sheets is attributed to fluctuating B–H bonds with relatively weak binding energies that can be removed using the method developed in this study.