Improved hydrogen storage properties of MgH2 by addition of Co2NiO nanoparticles

Abstract

A sample of MgH₂ and 10 wt% Co₂NiO was prepared by the ball milling technique. The hydrogen storage properties and reaction mechanism of the sample were examined. The temperature-programmed desorption result shows that the addition of 10 wt% Co₂NiO to MgH₂ exhibited a lower onset desorption temperature of 300 °C, which was decreased to 117 and 70 °C compared to as-received and as-milled MgH₂, respectively. The de/rehydrogenation kinetics of MgH₂ + 10 wt% Co₂NiO showed improvement compared to un-doped MgH₂. The results of the Kissinger plot shows that the activation energy for the hydrogen desorption of MgH₂ was reduced to about 65.0 and 15.0 kJ mol⁻¹ compared to as-received and as-milled MgH₂, respectively. Meanwhile, the X-ray diffraction analysis shows the formation of a new phase of Mg–Co alloy and Co_1.29Ni_1.71O₄ after the dehydrogenation and rehydrogenation process. It is reasonable to conclude that the Co₂NiO additive plays a catalytic role through the formation of active species of Mg–Co alloy and Co_1.29Ni_1.71O₄ during the heating process, thus improving the hydrogen storage properties of MgH₂.