Ruthenium-Functionalized Carbyne Rings for Near-Ambient Reversible Hydrogen Storage: A Density Functional Theory Study

Development of efficient and reversible hydrogen storage materials remains a critical challenge for fuel cell technologies. Using density functional theory with van der Waals corrections (DFT-D), we evaluate the hydrogen storage potential of ruthenium-decorated carbyne (C₁₀) rings. Structural carbyne configurations are considered: cumulene-type (A) and polyyne-type (B). A single Ru atom binds strongly to the carbyne framework, with binding energies of 3.57 eV (A) and 3.72 eV (B), ensuring thermodynamic stability and preventing metal clustering. Sequential H₂ adsorption reveals that each Ru center can capture up to 6H₂ molecules, with adsorption energies of 0.22–0.45 eV per H₂ (average 0.37–0.40 eV), characteristic of Kubas-type interactions. The system achieves a material-level gravimetric capacity of 5.18 wt.%, approaching the U.S. Department of Energy's 2025 interim target of 5.5 wt.% for complete onboard systems. Desorption temperatures estimated via the van't Hoff equation range from 204 K to 271 K depending on pressure and configuration, indicating facile hydrogen release near room temperature. Molecular dynamics simulations confirm the thermal stability of the RuC₁₀–6H₂ complex and reversible H₂ desorption at 300 K. These findings establish Ru-decorated carbyne rings as a promising candidate for practical hydrogen storage in fuel cells, providing a strong foundation for future experimental validation.