One of the potential ways to store H2 is the synthesis of metal hydrides, i.e., compounds of metals with hydrogen. Among these compounds is magnesium hydride (MgH2), with a hydrogen concentration of 7.66%. For hydrogen extraction, this compound must be heated to 400 degrees Celsius, which makes it difficult to use this method at a commercial level.
The scientists from Tomsk Polytechnic University have made an attempt to reduce the desorption temperature by creating a new composite material in which nickel nanoparticles obtained by electrically exploding conductors were used as an additive to magnesium hydroxide. The authors mixed the resulting nanopowder with magnesium hydride using a planetary ball mill (a device for ultrafine grinding of materials), obtaining a structure in which magnesium serves as the core and nanonickel acts as the shell.
The new composite has made it possible to reduce the temperature of hydrogen desorption from magnesium hydride to 150 degrees Celsius. This is caused by the weakening of the magnesium-hydrogen bonds in the presence of nickel atoms and the formation of intermetallics, i.e., compounds of two metals that act as a hydrogen pump. The latter case refers to the accelerated accumulation of hydrogen due to the expansion of the magnesium crystal lattice.
“The resulting composite can be used at temperatures below 150 °C, which makes it possible to use water as a coolant in a metal hydride hydrogen storage system, while the reversible capacity of the material stands at about 4 mass percent. As a point of comparison, the reversible capacity of LaNi5, an alloy of lanthanum and nickel, which is the most studied metal hydride for storing hydrogen to date, is 1–2 mass percent,” Viktor Kudiyarov, candidate of technical sciences, is quoted as saying by Tomsk Polytechnic University.
