## 1 Introduction  
Hydrogen is considered as an efficient, operationally convenient, and cost-effective energy resource for a clean future. These features of hydrogen have introduced hydrogen production and hydrogen storage techniques as an attractive field of study. In this regard, it is necessary to leverage and understand the full benefits of hydrogen application in the context of \"Hydrogen Economy\". For instance, the excess H\({}_{2}\) generated from other renewable energy resources such as solar energy and wind provide a wide range of economically efficient in possibilities in a \"power-to-gas\" vision.  
Clathrate hydrates, also known as gas hydrates, are composite compounds, in which water molecules form a lattice framework that are entrapped guest molecules in. This family of materials crystalize in three main structures [1]: types sl, sll and sH. Each polymorph is made by a different number of water molecules which form a different number of cages. For example, dual propane/hydrogen hydrate with sII type structure has a unit cell 136 water molecules form eight 5\({}^{12}6^{4}\) and sixteen 5\({}^{12}\) cavities. Propane can only be fitted in large (5\({}^{12}6^{4}\)) cavities, while smaller 5\({}^{12}\) cages are empty and have potential to entrap other small guest molecules, e.g., H\({}_{2}\), for physical gas storage application [2].  
Hydrogen hydrate crystallises in sII type hydrate form and at maximum can store hydrogen equivalent to 5.3 wt% of its total mass (mass H\({}_{2}\) per mass H\({}_{2}\)O) sII at 250 K and 2-3 kbar pressure [3; 4]. Indeed, this high-pressure demand acting as a limiting constraint on its practical application as a hydrogen-storage medium [5; 6; 7]. To solve this issue one approach can be employing binary hydrates with a \"helper\" molecule (liquid or gas) and hydrogen as the secondary compound, those are stable at milder conditions, e.g., at \(\sim\)30-50 bar and \(\sim\)280 K but with a substantially lower hydrogen-storage capacity [5; 6; 7; 8; 9].  
Apart from well-studied liquid-phase promoters such as THF hydrate [8; 9; 10] for sII H\({}_{2}\)-bearing hydrates, there have been studies on gas-phase promoters facilitation sII H\({}_{2}\)-containing clathrates. [PERSON] et al. investigated the possibility of having SF\({}_{6}\) as the helper compound in forming sII hydrate while hydrogen molecules can be stored in small cages. In their molecular simulation study, they have observed frequent diffusion of H\({}_{2}\) molecules between large cages, however, having SF\({}_{6}\) molecules in the large cages are limiting the diffusion. They proposed an optimal occupancy of large cages with SF\({}_{6}\) in which hydrate can stay stable while the maximum H\({}_{2}\) storage capacity can be obtained [11]. [PERSON] et al. found sII structured propane-hydrogen-mixed hydrate to be favourable for storing hydrogen with 0.33 wt% capacity at 270 K and 120 bar [12].  
In the present study, we have investigated H\({}_{2}\)- uptake and release kinetics through non-equilibrium molecular dynamics simulations at various temperatures, as well as experimentally forming propane hydrate and evaluating the experimental capacity of hydrogen storage into the formed propane hydrate.