###### Abstract
This one-dimensional diffusive mass-transport model is based on the equilibrium reactions among gas-water-rock interactions and kinetic reactions for sulfate reduction and methanogenesis. The main risk of underground H\({}_{2}\) storage in depleted gas fields predicted by HGCM is the conversion of hydrogen to methane, CH\({}_{4}\)(gas), and H\({}_{2}\)S\({}_{\text{(gas)}}\) due to microbial activity, gas-water-rock interactions in the reservoir, and the loss of aqueous hydrogen by diffusion through the cap rock brine. According to the results obtained from this one-dimensional modeling, the authors recommended that depleted gas fields for underground H\({}_{2}\) storage possess low residual CO\({}_{2}\)(gas) concentrations. Additionally, the mineralogical compositions of the reservoir rocks should contain low amounts of sulfate- and carbonate-bearing minerals, but high amounts of iron-bearing minerals. Metal hydrides employed as hydrogen storage systems, often demand the fulfillment of two important criteria such as thermodynamics and the kinetics. Though suitable alloying or mechanical milling can optimize the thermodynamics, the kinetics have intrinsic limitations, which require novel methods such as catalytic doping and nanoparticle formation, etc. [PERSON] et al. [10] employed a novel magnetic field and studied its effects on the thermal reaction kinetics of a metal hydride storage bed. Since the candidate metal hydrides such as lanthanum pentanickellide (LaNi\({}_{5}\)) and magnesium hydride (MgH\({}_{2}\)) are paramagnetic in nature, the effect of an external magnetic field on the heat conduction and reaction kinetics of such metal hydrides were investigated by the authors. The rapid heat transfer in a metal hydride bed was observed when these hydrides were subjected to magnetic fields of 3-5 kGauss or less than half a Tesla. Regarding hydrogen absorption, the capacity of metal hydrides with enhanced kinetics was obtained for a high-intensity magnetic field (0.5 T), however, poor kinetics was obtained for the samples subjected with no field (0 T) or a low-intensity field (0.3 T). Overall, the deployment of a magnetic field in a metal hydride storage test bed was found to enhance the reaction kinetics to due to the greater heat transfer and solid-gas reactions. Since the abovementioned metal hydrides have limitations in terms of hydrogen storage capacity (LaNi\({}_{5}\)\(<\)1.5 wt.% H\({}_{2}\)) and a faster sorption rate at moderate to high temperatures (MgH\({}_{2}\)\(\sim\)300 \({}^{\circ}\)C), a new class of complex hydrides with better temperature and hydrogen storage capacities were demonstrated by [PERSON] et al. [11]. The new complex hydrides, involving lithium amide and pre-processed magnesium hydride with different stoichiometric rations (xLiNH\({}_{2}\)-nanoMgH\({}_{2}\); x = 1, 2), were synthesized using a mechanochemical process under an inert or hydrogen ambient atmosphere. Another modification of the nano-catalyst additives on the base complex hydrides achieved faster desorption kinetics when compared to pristine (no catalyst additive) complex hydrides. Based on a detailed thermal gravimetric analysis (TGA) and thermal programed desorption (TPD), kinetics enhancement occurred in the following order of catalyst type: TiF\({}_{3}\)\(>\) nanoNi \(>\) nanoTi \(>\) nanoCo \(>\) nanoFe. Furthermore, the highest reduction of the on-set decomposition temperature was obtained in the order of nanoCo \(>\) TiF\({}_{3}\)\(>\) nanoTi \(>\) nanoFe \(>\) nanoNi. Additionally, the absorption kinetics of 2 wt.% nanoNi on the base complex hydride (2 LiNH\({}_{2}\)-nanoMgH\({}_{2}\)) was rapid (within the first 60 min of hydrogen absorption) at 200 \({}^{\circ}\)C when compared to the base material with no catalyst additive. The structural, microstructural, and chemical characterization supported the hydrogen sorption behavior of the complex hydrides.