Enhanced cyclic performance of MgH2/γ-MnS composite and evolution behavior of the sulfide.

In the present work, three kinds of γ-MnS with different morphologies were prepared by solvothermal method and employed to improve the hydrogen storage properties of MgH 2. It was found that spherical γ-MnS had the best catalytic activity. The influences of γ-MnS content and milling time on the hydrogen storage performance of MgH 2 were investigated. The initial hydrogen release of MgH 2 -5(γ-MnS)-5 h composite started at 241 ℃, 4.61 wt% of hydrogen was desorbed within 20 min at 270 ℃, and 4.24 wt% of hydrogen was absorbed within 10 min at 150 ℃. The apparent activation energies of hydrogen absorption and desorption of MgH 2 -5(γ-MnS)-5 h composite decreased to 45.1 and 63.6 kJ/mol, respectively. In addition, the composite also exhibited good cycle performance, which could keep stable in 60 cycles. The results of SEM and TEM declared that the catalyst was uniformly distributed on the matrix during the cycling process, and the worm-like morphology of the sample also had a positive effect on the stability of kinetics. XPS analysis of Mn 2p in the samples showed that only characteristic peaks of γ-MnS 2p were observed in the ball-milled samples, but the characteristic peaks of Mn 2p and α-MnS 2p were observed in the first and tenth hydrogenated samples, while only the peaks of Mn 2p were observed in the sixtieth hydrogenated sample. The formation of Mn not only greatly weakened the Mg-H bond, but also led to a slight increase in cycle capacity. Therefore, γ-MnS-doped MgH 2 manifested a good comprehensive hydrogen storage performance. [Display omitted] • The catalytic properties of γ-MnS with different morphologies were studied. • MgH2–5(γ-MnS) can desorb 4.61 wt% hydrogen within 20 min at 270 °C. • The cycle performance of MgH2–5(γ-MnS) remained stable during 60 cycles. • The evolution of γ-MnS was systematically clarified. [ABSTRACT FROM AUTHOR]