High-Capacity Reversible Hydrogen Storage in Yttrium-Decorated 2D Polyaramid: Adsorption and Desorption Mechanism from DFT Simulations

Achieving efficient hydrogen storage is a major challenge for the practical deployment of hydrogen as a clean energy carrier. Here, we investigate the hydrogen storage potential of yttrium-decorated two-dimensional polyaramid (Y-2DPA) using density functional theory (DFT) simulations. 2DPA, comprising alternating benzene and triazine units, is highly porous but unsuitable for hydrogen storage in its unmodified form. The incorporated Y adatoms stabilize strongly on the 2DPA lattice owing to high binding energy (−3.475 eV), and an ab initio molecular dynamics investigation and phonon dispersion analysis confirm the thermal and dynamical stability of the decorated structure. Each Y atom adsorbs up to seven H2 molecules within the optimal binding energy window (−0.2 to −0.7 eV/H2) prescribed by the U.S. Department of Energy (DOE). A maximum gravimetric capacity of 7.65 wt % is achieved for 3Y-2DPA, surpassing DOE targets. Climbing-image nudged elastic band (C-NEB) calculations reveal a desorption barrier of 0.658 eV, and pressure–temperature analysis indicates hydrogen release at 310–380 K under delivery pressures of 1–12 bar. Electronic structure and charge-density analyses highlight Kubas-type interactions, supplemented by polarization-assisted physisorption, as the dominant H2 binding mechanisms. These findings establish Y-2DPA as a robust and efficient material for H2 storage in fuel cell applications.