Synthesised Hydrocarbons
An alternative to hydrides is to use regular hydrocarbon fuels as the hydrogen carrier. Then a small hydrogen reformer would extract the hydrogen as needed by the fuel cell. However, these reformers are slow to react to changes in demand and add a large incremental cost to the vehicle powertrain.
Direct methanol fuel cells do not require a reformer, but provide a lower energy density compared to conventional fuel cells, although this could be counter balanced with the much better energy densities of ethanol and methanol over hydrogen. Alcohol fuel is a renewable resource.
Solid-oxide fuel cells can run on light hydrocarbons such as propane and methane without a reformer, or can run on higher hydrocarbons with only partial reforming, but the high temperature and slow startup time of these fuel cells makes them prohibitive for automobiles.
Direct methanol fuel cells do not require a reformer, but provide a lower energy density compared to conventional fuel cells, although this could be counter balanced with the much better energy densities of ethanol and methanol over hydrogen. Alcohol fuel is a renewable resource.
Solid-oxide fuel cells can run on light hydrocarbons such as propane and methane without a reformer, or can run on higher hydrocarbons with only partial reforming, but the high temperature and slow startup time of these fuel cells makes them prohibitive for automobiles.
Carbon nanotubes 
Hydrogen carriers based on nanostructured carbon (such as carbon buckyballs and nanotubes) have been proposed. Despite occasional claims of greater than 50 wt% hydrogen storage, it has generally come to be accepted that less than 1 wt% is practical.
Hydrogen carriers based on nanostructured carbon (such as carbon buckyballs and nanotubes) have been proposed. Despite occasional claims of greater than 50 wt% hydrogen storage, it has generally come to be accepted that less than 1 wt% is practical.
Metal-Organic Frameworks
Another class of synthetic porous materials that could store hydrogen efficiently are Metal-Organic Frameworks. In 2006, chemists at UCLA and the University of Michigan have achieved hydrogen storage concentrations of up to 7.5% weight in a Metal Organic Framework material. However, the storage was achieved at the low temperature of 77 Kelvin.
Polymer
Aug 4 2006 - A team of Korean researchers led by Professor Lim Ji-sun of Seoul National University’s School of Physics found a new material with the hydrogen storage efficiency of 7.6 percent based on first-principles electronic structure calculations for hydrogen binding to metal-decorated polymers of many different kinds, the hydrogen can be stored in solid matter in normal temperatures and pressures by attaching a titanium atom to a polyacetylene.
Glass microspheres
Hollow glass microspheres can be utilized for controlled storage and release of hydrogen.
Hydrogen-Storage Materials Based on Imidazolium Ionic Liquids
In 2007 Dupont and others reported Hydrogen-Storage Materials Based on Imidazolium Ionic Liquids. Simple alkyl(aryl)-3-methylimidazolium N-bis(trifluoromethanesulfonyl)imidate salts that possess very low vapour pressure, high density, and thermal stability and are not inflammable can add reversibly 6-12 hydrogen atoms in the presence of classical Pd/C or Ir0 nanoparticle catalysts and can be used as alternative materials for on-board hydrogen-storage devices. These salts can hold up to 30 g L-1 of hydrogen at atmospheric pressure, which is twice that compressed hydrogen gas can attain at 350
Hydrogen-Storage Materials Based on Imidazolium Ionic Liquids
In 2007 Dupont and others reported Hydrogen-Storage Materials Based on Imidazolium Ionic Liquids. Simple alkyl(aryl)-3-methylimidazolium N-bis(trifluoromethanesulfonyl)imidate salts that possess very low vapour pressure, high density, and thermal stability and are not inflammable can add reversibly 6-12 hydrogen atoms in the presence of classical Pd/C or Ir0 nanoparticle catalysts and can be used as alternative materials for on-board hydrogen-storage devices. These salts can hold up to 30 g L-1 of hydrogen at atmospheric pressure, which is twice that compressed hydrogen gas can attain at 350
Phosphonium borate
In 2006 researchers of University of Windsor reported on reversible hydrogen storage in a non-metal phosphonium borate .The phosphino-borane on the left accepts one equivalent of hydrogen at one atmosphere and 25°C and expels it again by heating to 100°C. The storage capacity is 0.25 wt% still rather below the 6 to 9 wt% required for practical use.
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