Hydrogen storage alloys. Divided into magnesium, rare earth and titanium hydrides, hydrogen storage alloys use metals or alloys to store hydrogen by reacting with it to form hydrides, a much safer way of storing hydrogen than using conventional physical storage methods. The stored hydrogen can then be released for use when the hydrides are heated. Some examples of these storage alloy hydrides are LaNi5, Mg2Ni, FeTi. Magnesium-based alloy hydrides have the most promising hydrogen storage properties. Intermetallic compounds such as TiFe and LaNi5 have good hydrogen storage reversibility. Recently, a new class of alloys, TiZrNbFeNi high-entropy alloys (HEA) were investigated for H2 storage. 99 100 LaNi5-based alloys have been used in practical applications because of their stable reversible hydrogen absorption and desorption reactions under moderate conditions (i.e., room temperature and hydrogen gas pressure less than 1 MPa).