The quest to make hydrogen the fuel of the future
Glossary
adsorption. The binding of molecules or particles to the surface of a solid or liquid, as opposed to absorption, the filling of pores within a solid. The binding to the surface is usually weak and reversible unless a chemical bond is formed.
algae. A large group of simple organisms, ranging from single celled phytoplankton to the larger seaweeds. Like plants they are photosynthetic, but they generally have a simpler structure than plants. Algae are found in water as well as on land.
biomass. Plant or animal matter (including agricultural waste) used as a fuel or energy source. Alternatively, the total mass of living matter within a given environmental area.
complex hydrides. Complex hydrides combine hydrogen with metals and other substances; they typically contain more than one type of metal or metalloid (eg. sodium aluminium hydride).
cryogenic. Relating to very low temperatures.
electrolysis. Chemical reactions brought about by passing electricity through a solution. The following equation illustrates the process of the electrolysis of water (H2O).
gasification. The conversion of a substance into a gas. The conversion of coal, petroleum or biomass into a gas mixture containing carbon dioxide, carbon monoxide and hydrogen in the presence of oxygen. The gas mixture produced (syngas) can then be treated with steam to produce more hydrogen. Gasification occurs through chemical reactions at high temperature and often at high pressure.
geothermal. Related to the heat emitted from the Earth; for example, hot springs are heated by geothermal sources. Geothermal energy is generated from natural steam, hot water, hot rocks or lava in the Earth's crust.
gigajoule. The joule (J) is a unit for measuring energy. A gigajoule is one thousand million (109) joules. It is defined as the work done, or energy expended, by a force of one newton moving one metre in the direction of the force.
metal hydrides. Compounds in which hydrogen is bonded chemically to a metal or metalloid (eg. boron or silicon).
metal-organic frameworks (MOFs). Compounds consisting of metal ions associated with organic (carbon-containing) molecules that form three dimensional porous structures. The pores allow storage of gases such as hydrogen by adsorption.
nanotubes. Extremely small tubes that can be made from pure carbon. For more information see IPE nanotube primer (Institut de Physique des Nanostructures, Switzerland).
photoelectrochemical cell. Light (eg. solar) cells that use semiconductors to capture light energy and convert it into electrical energy. The electrical energy is then used directly to produce hydrogen in a process similar to the electrolysis of water.
photosynthesis. The process in which green plants and some other organisms such as algae use energy from light to synthesise carbohydrates from carbon dioxide and water. Photosynthesis can be shown as:
CO2 + H2O + energy →[CH2O] + O2
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Posted September 2008.