Rational design of semi-interpenetrating network based on hyperbranched polyglycerol grafted MXene/polyurethane–epoxy for compressed hydrogen storage

Hydrogen (H₂) energy has emerged as a promising alternative in the automotive sector to replace fossil fuel; however, its storage with volumetric efficiency remains a challenge. The latest type IV storage vessel featuring a polymeric liner with composite overwrap incurs hydrogen saturation, which eventually causes failure. To prevent the H₂ dissolution in the liner, we have developed a barrier coating comprised of polyurethane/epoxy semi-interpenetrating network (S-IPN) combined with hyperbranched polyglycerol grafted MXene (h-MXene). The hyperbranched structure facilitated the dispersion of MXene in the coating solution by enhancing the exfoliation and improved the polymer filler interaction by forming covalent and H-bonding through end-terminal hydroxyl groups. Leveraging the dense network of S-IPN combined with the dispersed layer structured h-MXene significantly increased the tortuosity of the spray-coated barrier film applied to the nylon 6 liner. The coating exhibited a 90 % reduction in the H₂ gas permeability at only 2 wt% h-MXene concentration, which further improved to above 98 % at 10 wt% loading. Additionally, the h-MXene considerably improved the adhesion with the liner even in a highly stretched condition, signifying the durability of the coating under cyclic pressurization and depressurization of the storage vessel.