Catalytic effect of Si2BN monolayer on the dehydrogenation of MgH2: First-principles study

Many studies have shown that the catalysts containing B, N, and Si elements significantly enhance the dehydrogenation process of MgH2. In present work, the Si2BN monolayer was chosen as the catalyst, and its effect on the dehydrogenation of MgH2 nanoparticles was systematically studied using first-principles calculations. The calculated binding energy indicates that the Si2BN monolayer effectively prevents the agglomeration of Mg5H10 cluster. More importantly, all the dehydrogenation enthalpies for Mg5H10 significantly decrease due to the catalysis of Si2BN. The dehydrogenation energy barrier of Mg5H10 on the Si2BN substrate is reduced by 0.8 eV when H5+H6 is released from the cluster compared to the undoped case. Analysing the electron densities, electron transfer, and density of states, it was found that the intrinsic mechanism of the catalytic effect of Si2BN on the Mg5H10 cluster originates from the formation of Mg-Si and H-Si chemical bonds at the Mg5H10/Si2BN interface. These chemical bonds not only tightly restrain the Mg5H10 to prevent its agglomeration, but also enlarge Mg-H bonds from 1.91 & Aring; to 2.00 & Aring;, leading to easier hydrogen release. The research suggests that the Si2BN monolayer is a promising catalyst with the ability to inhibit agglomeration, thus enhancing the dehydrogenation properties of MgH2 clusters.