Excellent catalytic activity of two-dimensional Ti2C and Ti2CT2 (T = O, F, OH) monolayers on hydrogen storage of MgH2: First-principles calculations

Abstract

Two-dimensional Ti2C MXene has been recognized as an effective additive to improve the dehydrogenation of light metal hydride. Here, an MgH2 molecule adsorption on 2D Ti2C and Ti2CT2 monolayers were theoretically studied. Adsorption energy, the charge transfer and the electronic density of states were investigated via first-principles calculations based on density functional theory (DFT). We found that adopting bare Ti2C and functionalized Ti2CT2 to adsorb MgH2 molecule is not a good strategy. The charge transfer and DOS results revealed that bare Ti2C monolayer can enhance the dehydrogenation of MgH2 more effectively than functionalized Ti2CT2. Moreover, we have explored the catalytic mechanism of 2D Ti2C MXene on MgH2 using ab initio molecular dynamic (ab-init MD) simulations of MgH2/Ti2C heterostructure interface. It is found that the formation of TiH2 in Ti2C/MgH2 interface serves as a catalyst during the dehydrogenation of MgH2. Based on the analyses of electronic structure and the results of ab-init MD dynamic simulations, we found that the catalytic effects of 2D Ti2C MXene on MgH2 are presented in two aspects: as the electron e− transfer carrier and in-situ formed catalyst TiH2, they work together to enhance the dehydrogenation performance of MgH2.