Effects of Hydrogen Molecule Absorption on the Raman Scattering in Intrinsic and Decorated Graphene

The potential of hydrogen as a clean energy source critically depends on hydrogen storage efficiency, due to its environmentally friendly water byproduct, non-toxic nature, and absence of pollution. While many theoretical studies have explored hydrogen storage using 2D materials, fewer experimental studies have been undertaken. In this work, we investigated the effects of hydrogen pressure, number of layers, defect density, and types of metals used to decorate graphene on hydrogen storage efficiency in graphene. Graphene thin layers were prepared using the “scotch tape” method and exposed to molecular hydrogen gas. We monitored the hydrogen absorption on graphene using Raman spectroscopy at various conditions. In our experiments, the G peaks for graphene layers with different thicknesses were found to shift to lower wavenumbers with time upon hydrogen introduction. Notably, monolayer graphene exhibits the most significant red shift in the G peak. The 2D peak remains largely unaffected, exhibiting unobvious time-dependent variations. Defect density analysis under varying hydrogen pressures highlighted distinctions between pristine and defected graphene. Using similar methods on metal-decorated graphene and graphite generated from coal reveals further insight into the potential applications of modified graphite materials for hydrogen storage. Our findings underscore that specific Raman modes offer a promising avenue for determining hydrogen storage efficiency in 2D materials.