Thermodynamic and electrochemical properties of nanocrystalline Mg_2Cu-type hydrogen storage materials

摘要

Mechanical alloying (MA) process was used to synthesize the nanocrystalline Mg_2Cu and nanocomposite Mg_2Cu/Pd hydrogen storage materials. The structure of these materials has been examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermodynamic and electrochemical properties have also been investigated. The mechanical alloying for 18 h led directly to the formation of the orthorhombic-type structure with a crystallite sizes of about 30 nm. The results show that the maximum absorption capacity reaches 2.25 wt. percent for nanocrystalline Mg_2Cu alloy. This is lower than in the polycrystalline Mg_2Cu alloy (2.6 wt. percent) because of a significant amount of strain, chemical disorder and defects introduced into the material during the mechanical alloying process. On the other hand, mechanically coated Mg_2Cu alloy with palladium has effectively reduced the degradation rate of the studied electrode material.