Hydrogen compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways that seldom involve elementary hydrogen. Compounds of hydrogen are often called hydrides, a term that is used fairly loosely. The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H, and is used when
Hydrogen storage technology. As of 2010, the BMW Group has started a thorough component and system level validation of cryo-compressed vehicle storage on its way to a commercial product. Hydrogen carriers based on nanostructured carbon (such as carbon buckyballs and nanotubes) have been proposed. However, since Hydrogen usually amounts up to ~3.0-7.0 wt% at 77K which is far from the value set by US department of Energy (6 wt% at nearly ambient conditions), it makes carbon materials poor candidates for hydrogen storage. To realize carbon materials as effective hydrogen storage technologies, the Clean Energy Research Center has doped carbon nanotubes (CNTs) with