Hydrogen adsorption on titanium- and strontium-decorated graphene using first-principles study

Abstract

The widespread adoption of hydrogen fuel is heavily constrained by the lack of efficient storage materials. Graphene offers exceptional physical properties for high-capacity storage; however, its pristine surface lacks the active sites necessary for strong chemical binding. Although introducing metal decoration for the graphene is a known strategy to enhance surface reactivity, the complex interplay between the dopant, the carbon lattice, and hydrogen requires atomic-level clarification. Using density functional theory (DFT), we evaluated the electronic structure and adsorption energies of titanium- and strontium-decorated graphene monolayers upon hydrogen exposure. Hydrogen adsorption energies show unfavorable adsorption with pristine graphene (+0.33 eV), indicating weak physisorption. In contrast, Ti-decorated graphene exhibits strong chemisorption with a highly negative adsorption energy (−2.81 eV), while Sr-decorated graphene shows moderate binding (−0.92 eV), suggesting a balance between adsorption strength and reversibility. These results indicate that Ti-graphene enhances hydrogen adsorption capability but may hinder reversibility due to overly strong binding, whereas Sr-graphene provides more favorable storage conditions within a more moderate adsorption.