Ni_0.6Zn_0.4O Synthesised via a Solid-State Method for Promoting Hydrogen Sorption from MgH₂

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Magnesium hydride (MgH2) is a promising hydrogen storage material due to its high capacity (7.60 wt.%) and good reversibility.
• However, high desorption temperatures (>400 °C) and slow kinetics hinder practical applications of MgH2.
• Developing effective strategies to improve MgH2's hydrogen sorption properties is crucial for its widespread adoption.

Purpose of the Study:

• To synthesize nickel zinc oxide (Ni0.6Zn0.4O) and investigate its effect as a dopant in MgH2.
• To overcome the limitations of MgH2, specifically its high desorption temperature and slow sorption kinetics.
• To evaluate the catalytic impact of Ni0.6Zn0.4O on the hydrogen storage performance of MgH2.

Main Methods:

• Nickel zinc oxide (Ni0.6Zn0.4O) was synthesized using a solid-state method.
• Ni0.6Zn0.4O was doped into MgH2 at a concentration of 10 wt.%.
• Hydrogen sorption properties, including desorption temperature, kinetics, and activation energy, were analyzed for the composite material.

Main Results:

• The onset desorption temperature of MgH2-10 wt.% Ni0.6Zn0.4O was reduced by 133 °C and 56 °C compared to pure and milled MgH2, respectively.
• The composite absorbed 6.50 wt.% H2 at 250 °C and desorbed 2.20 wt.% H2 at 300 °C within 1 hour.
• The activation energy for hydrogen desorption decreased from 133 kJ/mol for MgH2 to 97 kJ/mol for the doped sample.
• Morphological analysis showed smaller particle sizes in the doped samples.

Conclusions:

• Doping MgH2 with 10 wt.% Ni0.6Zn0.4O significantly improves its hydrogen storage characteristics.
• The in situ formation of NiO, ZnO, and MgO acts as a catalyst, lowering activation energy and onset desorption temperature.
• The enhanced MgH2-Ni0.6Zn0.4O composite shows improved sorption kinetics, making it a more viable option for practical hydrogen storage.