Light transition-metal anchoring enables ultrahigh-capacity hydrogen storage in boron-graphdiyne monolayer

The development of efficient hydrogen (H₂) storage materials and strategies is crucial for enabling H₂ fuel cell vehicles and reducing dependence on fossil fuels in transportation. Boron-graphdiyne (BGDY), a member of the carbon-based materials family with an excellent and uniformly distributed pore size, has inspired us to explore its structural, electronic, metal-binding, and H₂ storage properties. In this regard, our dispersions-corrected spin-polarized density functional theory (DFT) calculations reveal that light transition metals (LTMs), such as Sc, Ti, V, and Cr, bind to the monolayer with binding energies of −3.79, −4.05, −3.32, and −2.00 eV, respectively. The binding of LTMs to the BGDY shifts the bandgap from semiconducting to metallic, which enhances the material's electronic properties. Upon binding, the LTMs lose charges to the BGDY, which renders them partially positive and, as a consequence, tailored for H₂ storage. The calculated H₂ adsorption energies fall within the optimal range of −0.15 to −0.60 eV, indicating favorable reversible binding. As a result, LTMs decorated BGDY efficiently anchors multiple H₂ molecules per metal site, leading to H₂ storage capacities of 14.04, 17.26, 14.86, and 11.46 wt% for Sc-, Ti-, V-, and Cr-doped BGDY, respectively. These values exceed the criteria for U. S DOE of 5.50 wt% set in 2025. Moreover, they exceed other materials in storage capacities such as graphene, graphydiyne, C2N, graphene, graphyne, and silicene. Thermodynamic analysis was employed to evaluate the H₂ desorption behavior under practical operating conditions. The results indicate that all systems are capable of desorbing H₂ within feasible temperature and pressure ranges.