Advancing hydrogen storage with functionalized carbon nanoribbons

This work investigates the hydrogen (H₂) storage potential of recently synthesized carbon nanoribbons (CNRs) using first-principles density functional theory (DFT) simulations. The weak interaction of H₂ with pristine CNRs is significantly enhanced upon functionalization with light metals (Li, Na, K, Mg, and Ca), all of which form strong bonds with the nitrogen-substituted nanoribbons (N-CNRs). H₂ adsorption energies on metal-functionalized N-CNRs range from −0.597 eV/H₂ (Li) to −0.110 eV/H₂ (Mg). Theoretical gravimetric storage capacities (G_t) reached up to 7.08 wt% (Li), with practical storage (G_p) values of 6.37 wt% (Li), 5.69 wt% (Na), 5.28 wt% (Mg), 5.08 wt% (K), and 3.74 wt% (Ca) under practical adsorption (30 atm, 298.15 K) and desorption (3 atm, 373.15 K) conditions. H₂ desorption temperatures range from 140.68 K (Mg) to 763.54 K (Li), and corresponding H₂ recovery times varied from 7.04 × 10⁻¹¹ s (Mg) to 1.06 × 10⁻² s (Li). Thermodynamic stability analyses have confirmed the negative adsorption enthalpies at 0 K and the retention of stability up to 298 K at 100 atm for most systems. These results demonstrate the potential of metal-doped N-CNRs to meet or exceed the U.S. DOE target of 5.5 wt% H₂ storage at room temperature and moderate pressure, highlighting their practical suitability for solid-state H₂ storage systems.