Two-dimensional Sc_2C: A reversible and high-capacity hydrogen storage material predicted by first-principles calculations

摘要

Recently, a new family of two-dimensional (2D) MXene materials was prepared by exfoliating the MAX phases (ACS Nano 2012, 6, 1322). Among all possible MXene phases, theoretically 2D Sc_2C possesses the highest surface area per weight and thus is expected to have the highest gravimetric hydrogen storage capacities. In this work, using first-principles total energy pseudopotential calculations, we systematically investigated the hydrogen storage properties of 2D Sc_2C phase. Depending on different adsorption sites, the hydrogens are bound by three modes: chemisorption, physisorption and Kubas-type interactions with the binding energies of 4.703, 0.087 and 0.164 eV respectively. The maximum hydrogen storage capacity was calculated to be 9.0 wt.%, which meets the gravimetric storage capacity target (5.5 wt.% by 2015) set by the U.S. DOE. Ab-initio molecular dynamic simulations confirmed that 3.6 wt.% hydrogen molecules storaged by Kubas-troe interactions can be adsorbed and released reversiblv at ambient conditions.