the most effective being ruthenium. This catalysis works through chemisorption, where the adsorption energy of N2 is less than the reaction energy of dissociation. Hydrogen purification can be achieved in several ways. Hydrogen can be separated from unreacted ammonia using a permeable, hydrogen-selective membrane. It can also be purified through the adsorption of ammonia, which can be selectively trapped due to its polarity. In September 2005 chemists from the Technical University of Denmark announced a method of storing hydrogen in the form of ammonia saturated into a salt tablet. They claim it will be an inexpensive and safe storage method. positive and negative attributes of Ammonia ·pro's:High theoretical energy density, Wide spread availability, Large scale commercial production, Benign decomposition pathway to H2and N2 ·con's:Toxicity, Corrosive, High decomposition temperature leading to efficiency loss Hydrazine Hydrazine breaks down in the cell to form nitrogen and hydrogen/ Silicon hydrides and germanium hydrides are also candidates of hydrogen storage materials, as they can subject to energetically favored reaction to form covalently bonded dimers with loss of a hydrogen molecule. Chemical hydrides Chemical hydride is an irreversible hydrogen storage material. The reaction of hydrogen releasing from chemical hydrides are usually exothermic, which makes regeneration of the fuel energy-intensive. NaBH4 + 2H2O → NaBO2 + 4H2 + 300 kJ. The chemical reaction gives potential for high density storage, but current systems produce much lower effective density. The NaBH4 has a theoretical effective density of 10.8 wt.%, however there is only 1.1 wt.% of effective density in reality. Examples of chemical hydride reactions: NaBH4 (20~35% solution, stabilized with 1~3% NaOH) + 2H2O (from fuel cell exhaust) → NaBO2 (Borax in NaOH) + 4H2. 2LiH + 2H2O → 2LiOH + 2H2. A leading chemical hydride is NH3BH3, which is a waxy solid at room temperature with a melting point of 90 °C. Hydrogen will be released from NH3BH3 around 90 °C because of thermal decomposition. NH3BH3 is a promising material for hydrogen storing because it has one of the highest theoretical hydrogen weight percentages at 19.6% and also the highest hydrogen volume density at 151 kg H2 per volume. Hydrogen release from NH3BH3 occurs stepwise, where the onset temperature for the first equivalent is 90 °C, the temperature for second equivalent is 150 °C. The remaining hydrogen will be released at the temperature higher than 150 °C. Amine boranes Prior to 1980, several compounds were investigated for hydrogen