A Potential Hydrogen-Storage Media: C₂H₄ and C₅H₅ Molecules Doped with Rare Earth Atoms

Using first-principles calculations, we predict that a single C₂H₄ or C₅H₅ molecule can form a stable complex with two rare earth metals such as La, Eu, and Ho. The La₂C₂H₄ complex then absorbs up to sixteen hydrogen molecules, reaching a gravimetric storage capacity of 9.5wt% by adding a rare-earth metal atom, The results show that Eu-4f electrons have little impact on the hydrogen adsorption. The nature of bonding between Eu and H₂ is due to the hybridization of Eu-5d with the H-1s orbital.