Jump to Navigation

Magnesium

Magnesium is one of the main candidates for hydrogen storage, mainly because of its low price, availability and high gravimetric capacity of above 6 wt.%.

Used without a catalyst, however, magnesium exhibits the disadvantages of high operating temperature and slow kinetics. Thus the developpment of an applicable catalyst is very significant

Without catalysis, magnesium hydride forms does not form easily and, even at 350 and 400oC, the reaction is slow and difficult to complete.

In our experiments, magnesium powder was intermixed by a brief ball milling with one of our catalytic compounds and the catalyzed sample was exposed to hydrogen at room temperature under hydrogen pressure of 10 bars, without any preheating or activation. The immediate hydrogen uptake of the magnesium sample occurred, ultimately reaching over 6.5 wt.% capacity. After hydrogenation, the material exhibited an x-ray diffraction pattern characteristic for MgH2.


Catalyzed Magnesium Preparation

starting material:  commercial Mg shavings

 Magnesium shavings     

    Ball milling, before        

before and after ball milling


SEM micrograph of ball-milled magnesium powder    SEM micrograph of catalyst particle on magnesium powder   

          ball milled Mg                    catalyst particle on Mg powder

 Catalyzed magnesium

catyzed magnesium


Hydrogen Absorption by the Catalyzed Magnesium

           

Absorption in excess of 6 wt.% at room temperature

        

 


 

Complete hydrogenation at room temperature:

formation of magnesium hydride MgH2

x-ray diffraction confirmation of the reaction completion

 


 

 Reversible cyling of the Catalyzed Magnesium Hydride

Reversible Hydrogen Storage Material

 

 

  • Hydrogen capacity : > 6 wt.%
  • Re-hydrogenation can be done at any temperature between RT and above
  • Very low cost and abundant availability of the material
  • High stability of the hydride = indefinite storage without losses or boil off

 


Magnesium - based hydrogen storage systems

Mg -Ni, Mg-Al etc.

 

 

lower temperature of operation at the cost of reduced capacity as compared to pure MgH2

 

 


Other examples of Mg - based systems

 

 Mg - Na system

 

Mg Na magnesium sodium graph

 

MgH2 + NaH  ⇒  NaMgH3       (6 wt.%)


 

Mg - Ti system

Mg Ti magnesium titanium diffraction

Mg – Ti system  - immiscible,  - no equilibrium phases

Formed a metastable fcc  phase within a certain range of compositions

   

Mg Ti absorption

Absorption at room temperature of a catalyzed Mg-Ti sample

 

Mg-Ti hydrogenated diffraction

 

Fcc phase – absorbed hydrogen without crystallographic  transformation

 Hydrogenated phase is imilar to TiH2 but desorbs just above 200oC (instead of 600oC).

 


Please contact us with inquires related  to purchase of our hydrogen generators, catalysts or catalyzed materials at contact@hydrogenlink.com

 


Read more



by Dr. Radut.