What Is a Metal Hydride?

Composition and Uses of Metal Hydrides

Nickel metal hydride (NiMH) batteries are cheap, rechargeable and perform well in high-drain electronic devices. Photo &copy EIGHTFISH

Metal hydrides are metals which have been bonded to hydrogen to form a new compound. Any hydrogen compound that is bonded to another metal element can effectively be called a metal hydride. Generally, the bond is covalent in nature, but some hydrides are formed from ionic bonds. The hydrogen has an oxidation number of -1. The metal absorbs the gas, which forms the hydride. 

Examples of Metal Hydrides

The most common examples of metal hydrides include aluminum, boron, lithium borohydride and various salts.

For example, aluminum hydrides include sodium aluminum hydride. There are also many more complex metal hydrides suitable for various uses.

Uses for Metal Hydrides

Metal hydrides are often used in fuel cell applications that use hydrogen as a fuel. Nickel hydrides are often found in various types of batteries, particularly NiMH batteries. Nickel metal hydride batteries rely on hydrides of rare earth intermetallic compounds, such as lanthanum or neodymium bonded with cobalt or manganese. Lithium hydrides and sodium borohydride both serve as reducing agents in chemistry applications. Most hydrides behave as reducing agents in chemical reactions.