Effects of Hydrogen Molecule Absorption on the Raman Scattering in Few-layer Graphene

Hydrogen storage is vital for the future of clean energy, given its environmentally friendly water byproduct, non-toxic nature, and absence of pollution. While many studies have been dedicated to enhancing efficiency in graphene oxides, intrinsic graphene remains an intriguing storage platform awaiting further exploration. In this work, we investigate the effects of hydrogen pressure, number of layers and defect density of graphene on hydrogen storage efficiency. We prepared graphene thin layers using the "scotch tape" method and then exposed them to molecular hydrogen gas, monitoring the absorption via Raman spectroscopy. We find that the G peaks for graphene layers with different thicknesses shift to a lower wavenumber with time upon hydrogen introduction. Notably, monolayer graphene exhibits the most significant red shift in the G peak. Conversely, the 2D peak remains largely unaffected, exhibiting unobvious time-dependent variations. Furthermore, our defect analysis under varying hydrogen pressures accentuates the distinction between pristine and defected graphene. Our findings underscore that specific Raman modes offer a promising avenue for determining hydrogen storage efficiency in 2D materials.