Hydrogen storage in MXenes: Controlled adjustment of sorption by interlayer distance and transition metal elements

MXene is an attractive solid-state material for high-capacity, secure hydrogen storage under ambient conditions. Controlled adjustment of hydrogen sorption in MXene is essential to improve the storage capability and reversibility at room temperature. This study employed first-principles calculations to investigate the hydrogen sorption properties of multilayered MXenes at the electron level. The strong physical adsorption (Kubas type) of hydrogen was observed in MXene. The interlayer distance and the transition metal elements of MXenes allowed adjustment of the sorption energy of hydrogen. The narrow interlayer space benefited the adsorption of hydrogen molecules, instead of hydrogen atoms. Group 4B elements enhanced the chemical absorption, while Hf2C and Ta2C MXenes possessed relatively strong physical adsorption of hydrogen molecules. Furthermore, the density of states, d-band center, and electron density difference were used to reveal the electronic properties of MXene-hydrogen system.