How are elements like palladium able to store hydrogen reversibly? What is the name of this process ?
Hydrogen atoms can be stored using elements like palladium, platinum, etc. This process is called adsorption. It leads to the formation of the metal hydride.
Using methods such as imaging with a scanning tunneling microscope of palladium which has adsorbed hydrogen, scientists believe the adsorption is due to the hydrogen atoms accommodating themselves in vacant spaces between the metal atoms. Adsorption allows the storage of a large volume of hydrogen using a very small volume of the metal. For example, in the case of palladium, 1 cm^3 of the metal can store up to 900 cm^3 of hydrogen.
This property makes adsorption a very attractive method to store hydrogen for its use in fuel cells and for other purposes, without having to liquefy it under very high pressures and very low temperatures.