Computational Characterization of Advanced Hydrogen Storage Architecture Using Transition-Metal-Functionalized C3N5 Monolayers

Hydrogen (H₂) serves as a promising clean energy carrier due to its ultrahigh energy density, natural abundance, and environmental sustainability. However, its practical use remains limited by inefficient storage technologies. Material-based H₂ storage offers an attractive alternative to conventional high-pressure and cryogenic methods that raise practicality and safety concerns. This study explores the potential of two-dimensional (2D) carbon nitride (C₃N₅) monolayers functionalized with transition metals (TMs; Sc, Ti, and V) as candidate materials for effective H₂ storage. Using density functional theory (DFT), ab initio molecular dynamics (AIMD), and statistical thermodynamic analysis, we demonstrate the exceptional H₂ storage capabilities of this system. Up to four TMs (Sc, Ti, and V) were stably adhered onto C₃N₅ monolayers, exhibiting strong average binding energies of −5.92, −5.75, and −5.89 eV per dopant, respectively, exceeding the cohesive energies of their corresponding bulk metals. AIMD simulations confirmed structural stability at 400 K. Each dopant efficiently adsorbed multiple H₂ molecules through electrostatic and van der Waals interactions, achieving exceptional theoretical gravimetric storage capacities (at 0 K) of 9.65, 9.48, and 9.32 wt % for Sc, Ti, and V doping, respectively, surpassing the U.S. Department of Energy’s 2025 target of 5.50 wt %. The average binding energy of H₂ molecules falls within the optimal range (−0.20 to −0.60 eV), ensuring reversible adsorption and desorption under practical operating conditions, as validated by thermodynamic analyses based on the Langmuir adsorption model. Overall, TM-functionalized C₃N₅ is an auspicious material for advanced H₂ storage applications.