<h1>Hydrogen Fuel&nbsp;</h1> <h2>Context:</h2> <ul><li>Under ‘Mission Net Zero Carbon Emission Railway’ by 2030,&nbsp;Indian Railways are set to run trains on hydrogen fuel-based technology.&nbsp;For this, it is considering retrofitting of existing trains.</li></ul> <h2>Hydrogen Fuel:</h2> <ul><li class="ql-align-justify">Hydrogen is the lightest and first element on the periodic table. Since the weight of hydrogen is less than air, it rises in the atmosphere and is therefore rarely found in its pure form, H2 </li></ul> <ul><li class="ql-align-justify">At standard temperature and pressure, hydrogen is a nontoxic, nonmetallic, odorless, tasteless, colorless, and highly combustible diatomic gas </li></ul> <ul><li class="ql-align-justify">Hydrogen fuel is a zero-emission fuel burned with oxygen. It can be used in fuel cells or internal combustion engines. It is also used as a fuel for spacecraft propulsion </li></ul> <ul><li class="ql-align-justify">Hydrogen can be stored physically as either a gas or a liquid. Storage of hydrogen as a gas typically requires high-pressure tanks </li></ul> <ul><li class="ql-align-justify ql-indent-1">Storage of hydrogen as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one-atmosphere pressure is −252.8°C </li></ul> <ul><li class="ql-align-justify ql-indent-1">Hydrogen can also be stored on the surfaces of solids (by adsorption) or within solids (by absorption)</li></ul>