Theoretical and Experimental Studies of Al-Impurity Effect on the Hydrogenation Behavior of Mg

Improvement of the Hydrogen Storage Characteristics of MgH2 with Al Nano-Catalyst Produced by the Method of Electric Explosion of Wires

A new composite with a core-shell structure based on magnesium hydride and finely dispersed aluminum powder with an aluminum oxide shell was mechanically synthesized. We used magnesium chips to produce magnesium hydride and aluminum wire after exploitation to produce nano-sized aluminum powder. The beginning of the hydrogen release from the composite occurred at the temperature of 117 °C. The maximum desorption temperature from the MgH2-EEWAl composite (10 wt.%) was 336 °C, compared to pure magnesium hydride-417 °C. The mass content of hydrogen in the composite was 5.5 wt.%. The positive effect of the aluminum powder produced by the electric explosion of wires method on reducing the activation energy of desorption was demonstrated. The composite's desorption activation energy was found to be 109 ± 1 kJ/mol, while pure magnesium hydride had an activation energy of 161 ± 2 kJ/mol. The results obtained make it possible to expand the possibility of using magnesium and aluminum waste for hydrogen energy.

Microstructure Characteristics and Hydrogen Storage Kinetics of Mg77+xNi20-xLa3 (x = 0, 5, 10, 15) Alloys

Mg_77+xNi_20-xLa₃ (x = 0, 5, 10, 15) alloys were successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction and scanning electron microscope. The effects of nickel content on the microstructure and hydrogen storage kinetic of the as-cast alloys were investigated. The results showed that the alloys are composed of a primary phase of Mg₂Ni, lamella eutectic composites of Mg + Mg₂Ni, and some amount of LaMg₁₂ and La₂Mg₁₇. Nickel addition significantly improved the hydrogen-absorption kinetic performance of the alloy. At 683 K, Mg₇₇Ni₂₀La₃ alloy and Mg₈₂Ni₁₅La₃ alloy underwent hydrogen absorption and desorption reactions for 2 h, respectively, and their hydrogen absorption and desorption capacities were 4.16 wt.% and 4.1 wt.%, and 4.92 wt.% and 4.69 wt.%, respectively. Using the Kissinger equation, it was calculated that the activation energy values of Mg₇₇Ni₂₀La₃, Mg₈₂Ni₁₅La₃, Mg₈₇Ni₁₀La₃ and Mg₉₂Ni₅La₃ alloys were in the range of 68.5~75.2 kJ/mol, much lower than 150~160 kJ/mol of MgH₂.