A DFT study on the outstanding hydrogen storage performance of the Ti-decorated MoS2 monolayer

Abstract

The hydrogen storage performances of the pure MoS2 monolayer and the one decorated with Ti atoms were studied via the first-principles DFT calculations. The Ti atom was calculated to be successfully and chemically decorated on the surface of MoS2 monolayer with a large binding energy of -4.979 eV, the absolute value of which was higher than the cohesive energy of Ti bulk (4.85 eV). The hydrogen molecule interacted weakly with the pure MoS2 with a low adsorption energy of only -0.0226 eV but was strongly adsorbed on the introduced active site of the Ti atom in the decorated MoS2 with an improved adsorption energy of -0.472 eV. There were four hydrogen molecules in maximum stored on the modified MoS2 monolayer via chemical interactions with an average adsorption energy being -0.413 eV. Moreover, the adsorbed hydrogen molecules released 1.29 e to the substrate of decorated MoS2 during the storage process. The stored hydrogen molecules of the MoS2 decorated with two Ti atoms were further improved to be eight with transferred charges being 2.42 e. Finally, the gravimetric density of hydrogen storage of the Ti-decorated MoS2 with a full coverage being 1 on its both sides could be enhanced to be as high as 5.93 wt%, well meeting the criteria of the United States Department of Energy. Our research indicates that the MoS2 monolayer decorated with Ti atoms is promising to effectively store the hydrogen molecules and is potentially applied as an excellent hydrogen gas sensor.