Abiola Ganiyat Olatoye,Jie Zhang,Qianyu Wang,Erping Cao,Wenli Li,Emmanuel Oluwaseyi Fagbohun,Yanbin Cui
In the present work, nanoporous carbon (NPC) was prepared from a metal–organic framework (zeolite imidazolate framework 8, ZIF-8). Different concentrations of graphene oxide (GO) were used to make NPC/reduced graphene oxide (NPC/rGO-x, x = 0.5, 1.0, 1.5, and 2.0) composites, and then γ-MnS/NPC/rGO-1 composite was synthesized via a simple hydrothermal technique. The electrochemical characteristics of porous carbon composites (NPC/rGO-x) and γ-MnS/NPC/rGO-1 electrodes were investigated by galvanostatic charge and discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. NPC/rGO-1 showed the highest specific capacitance of 207 F/g at 0.5 A/g. Also, the γ-MnS/NPC/rGO-1 electrode demonstrates exceptional electrochemical performance with a high specific capacitance of 300 F/g at 0.5 A/g and impressive cyclic stability of 70% capacitance retention after 10,000 cycles at 1 A/g. As a result, this study demonstrates that γ-MnS/NPC/rGO-1 electrode can be considered a promising candidate for high-performance supercapacitors.
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.
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