Hydrogen storage materials for vehicular applications

Abstract Hydrogen energy has been assessed as the clean and renewable energy source with the highest energy density. At present, 25% of energy demand comes from the transport sector, while 20% of greenhouse gases are produced from the transport sector at the global level. Hydrogen may be utilized in the vehicles as a fuel for fuel cell vehicles or as a hydrogen system in internal combustion engine vehicles. In both cases, hydrogen storage remains a key parameter. Various types of hydrogen storage materials have a wide range of operating conditions in terms of temperature, hydrogen plateau pressure, and hydrogen storage capacity with other relevant hydrogenation characteristics. At present, not a single hydrogen storage material is available to fulfill all the requirements of hydrogen storage for vehicles on the set target of DOE US. MgH 2 has high hydrogen storage capacity equivalent to 7 wt%, but desorption temperature is 300°C. The normal vehicles do not operate at such a high temperature. Therefore, in the present communication, combinations of metal hydrides have been studied. The first combination belongs to MgH 2 and AB 2 system and another belongs to MgH 2 , NaAlH 4 , and AB 2 system. In the calculation performed, it has been shown that the amount of heat and temperature available in the exhaust gas of a vehicle is enough to liberate the hydrogen from the high‐temperature metal hydride system. The calculated specific capacity on the system basis has been found as 1.13 kWh/kg (0.034 kgH 2 /kg) and 1.20 kWh/kg (0.036 kgH 2 /kg) for both combinations, respectively. These values of specific capacity are very much close to the present target of DOE US.