Hydrogen Confinement in Hexagonal Boron Nitride Bubbles Using UV Laser Illumination

Hexagonal boron nitride (h-BN) bubbles are of significant interest to micro-scale hydrogen storage thanks to their ability to confine hydrogen gas molecules. Previous reports of h-BN bubble creation from grown h-BN films require electron beams under vacuum, making integrating with other experimental setups for hydrogen production impractical. Therefore, in this study, the formation of h-BN bubbles is demonstrated in a 20 nm h-BN film grown on a sapphire substrate with a 213 nm UV laser beam. Using atomic force microscopy, it is shown that longer illumination time induces larger h-BN bubbles up to 20 µm with higher density. It is also demonstrated that h-BN bubbles do not collapse for more than 6 months after their creation. The internal pressure and gravimetric storage capacity of h-BN bubbles are reported. A maximum internal pressure of 41 MPa and a gravimetric storage capacity of 6% are obtained. These findings show that h-BN bubbles can be a promising system for long-term hydrogen storage.