Investigation on the effect of Co doping on structure, electronic, and hydrogen storage properties of Mg2FeH6

Metal hydrides, particularly magnesium-based materials, exhibit excellent hydrogen storage capabilities. Among these, Mg2FeH6 stands out for its high hydrogen storage capacity, but it faces limitations due to low thermodynamic stability and high hydrogen desorption temperature. To overcome these challenges, we investigated the potential of Co doping to improve hydrogen storage properties. Based on first-principles calculations, we systematically explored the structures, electronic properties and hydrogen storage capabilities of a novel Mg-Fe-CoH alloy. We found that Co doping significantly reduced the band gap by 1.14 eV, promoting electron transitions and accelerating hydrogen desorption kinetics. Additionally, Co doping alters the Fe-H interaction, increasing bond lengths and facilitating the hydrogen dissociation. Although Co doping slightly decreases hydrogen storage capability of Mg2FeH6 (from 5.45 wt% to 5.32 wt%), it significantly lowers desorption temperature from 651 K (Mg2FeH6) to 543 K (Mg2Fe1/8Co7/8H6). This study highlights the innovative potential of Co doping to enhance the performance of Mg2FeH6-based hydrogen storage materials, offering promising prospects for advancing hydrogen energy technologies.