Hydrogen Storage Techniques for Stationary and Mobile Applications: A Review

With the rapid increase of global warming and CO₂ emissions from conventional fuels, the world is seeking an international commitment from all-dominating countries for an emission cut down of about 55–60% till 2050. Molecular hydrogen is the most-favored chemical fuel alternative for both stationary and mobile applications. Hydrogen is the most efficient energy carrier known to us with the highest heating value per mass, i.e., 120–142 MJ/kg of all chemical fuels. Hydrogen also has the highest gross calorific value being 141.7 MJ/kg significantly higher than petrol 46.4 MJ/kg and diesel 45.6 MJ/kg for 0 °C at 1 bar. The production of hydrogen gas is a challenge itself. Water being the only by-product of the energy generation and zero emissions, hydrogen is regenerative and eco friendly. Gravimetric density and volumetric density are crucial for stationary and mobile applications. In this paper, the storage methods reviewed were high-pressure cylinder (upto 800 bars) using different metals and lightweight composite materials, storage of hydrogen in a liquid state using cryogenic tanks at 21 K, storage of hydrogen using the metal–organic framework and solid materials, chemical storage using covalent and ionic compounds, storage using selective few metals which possess property to absorb hydrogen excessively in large amount, storage that uses nanostructured based metal hydrides and absorption of hydrogen using carbon-based materials like Graphene. Hydrogen can also be stored indirectly in reactive metals using metal hydrides and chemisorptive techniques in Li, Na, Al, or Zn and other alkali elements.