Study on the thermodynamic stability and bonding mechanism of (Fe+Co) co-doped MgH₂ hydrogen storage materials

For exploring the effect of bimetallic co-doping on the hydrogen storage performance of MgH₂ hydrogen storage materials, the thermodynamic stability and bonding mechanism of (Fe+Co) co-doping MgH₂ hydrogen storage materials system were systematically studied by using first-principles calculations based on density functional theory.The lattice structure of the co-doped system was investigated, and found that the volume of Mg₁₂Fe₂Co₄H₃₆ and M-g₁₂Fe₄Co₂H₃₆ cell structure shrank by 16% and 17.5% respectively after (Fe+Co) co-doping.The formation enthalpy of the (Fe+Co) co-doping system was calculated, the calculated results reveal that the formation enthalpy of the system decreases after doping, which is more conducive to the resolution of hydrogen. The charge transfer of Fe and Co before and after doping and the bonding orbital between the metal atom and the hydrogen atom were investigated by calculating the Bader charge and electron density of states of the doping system, the analysis of the electronic structure proved that the electron transfer from the hydrogen atom to the magnesium atom after doping, which is beneficial to the weakening of the Mg—H bond. The (Fe+Co) bimetallic co-doping has a positive effect on the improvement of thermodynamic properties of MgH₂ hydrogen storage materials, which provides theoretical guidance for the development of high-performance hydrogen storage materials.