Employees at Moscow State University’s Faculty of Chemistry have improved the reaction of magnesium hydride with water, paving the way for the generation of hydrogen for use in fuel cells.
The addition of alkali metal, ammonium, and/or magnesium salts increases hydrogen yield from 22% to nearly 100%, while the hydrogen flow rate increases eightfold, according to the study’s authors.
Compact low-power fuel cells, such as chargers for electronics or power supply systems for consumers in remote and isolated locations, are powered by autonomous hydrogen sources. The interaction of a light metal (aluminum or magnesium) or its hydride with water is the most accessible way to obtain hydrogen for such sources. Hydrides are more efficient than metals on their own because they contain “their own” hydrogen, which is released in addition to hydrogen from water during the oxidation reaction. However, because aluminum, magnesium, and their hydrides interact with water so slowly under normal conditions, scientists are looking for ways to increase their reactivity.
Lyudmila Sevastyanova, Semyon Klyamkin, and Vladimir Stupnikov of the Laboratory of High Pressure Chemistry of the Department of Chemical Technology and New Materials of the Faculty of Chemistry of Moscow State University, led by the laboratory’s head Boris Bulychev, presented a new work. Its goal is to choose methods for preparing materials and simple aqueous solutions in such a way that their interaction produces the most hydrogen and moves at a fast enough speed.
To oxidize magnesium hydride, the researchers proposed using neutral salt solutions such as ammonium or magnesium chlorides and bromides. It is possible to achieve nearly 100% hydrogen yield in this reaction with their help without changing the acidity of the solution. Furthermore, the procedure is much quicker.
The mechanism of action of salts is still being researched. Insoluble hydroxides are most likely formed on the surface of the hydride during the reaction with water, preventing further water penetration and effectively stopping the reaction. Due to complexation, the presence of salts promotes the dissolution of these hydroxides or simply makes them more “loose.”
The authors intend to continue developing activation methods in future studies in order to expand the use of magnesium, aluminum, and their hydrides as relatively inexpensive and easy-to-find hydrogen generators.
