Embodiments provide rubber sealants and rubber sealant formulations for use in high pressure hydrogen storage and transportation. Example sealant formulations include mixtures of ethylene propylene diene monomers (EPDMs) or EPDM-like materials, optional thermally conductive fillers, optional hydrogen barrier fillers, reinforcing fillers, liquid rubbers, antioxidants, optional abrasion resistance additives, and curing agents (e.g., cross-linking agents). Example formulations are capable of peroxide curing to produce thermosetting elastomers with excellent thermomechanical properties. Example sealants provide very low equilibrium hydrogen concentrations and reduced swelling.