Abstract
The design of an excellent active catalyst to improve the sluggish kinetic and thermodynamic properties of magnesium hydride(MgH2)remains a great challenge to achieve its practical application.In this study,a novel Ni-Nb/rGO nanocomposite catalyst was successfully prepared by one-spot hydrothermal and sub-sequent calcination methods.The novel Ni-Nb/rGO nanocomposite exhibits an exceptional catalytic effect on improving MgH2 sorption properties.Specifically,the onset desorption temperature of MgH2+10 wt％Ni-Nb/rGO composite is reduced to 198 ℃,much lower than that of undoped MgH2(330 ℃).In-terestingly,the composite can release 5.0,5.9,and 6.0 wt％H2 within 10 min at 245,260,and 275 ℃,respectively.Furthermore,the dehydrogenated MgH2+10 wt％Ni-Nb/rGO composite starts to absorb hydrogen even at room temperature with approximate 2.75 wt％H2 uptake at 75 ℃ under 3 MPa H2 pressure within 30 min and exhibits excellent stability by maintaining 6.0 wt％hydrogen content after 20 cycles at 300 ℃.Chou's model suggests that the de/hydrogenation kinetics of Ni-Nb/rGO-modified MgH2 switches from surface penetration model to diffusion model at lower temperatures.Additionally,the ac-tivation energies(Ea)for the de/hydrogenation of MgH2+10 wt％Ni-Nb/rGO are reduced to 57.8 kJ/mol and 33.9 kJ/mol,which are significantly lower than those of undoped MgH2.The work demonstrates that the addition of a novel ternary Ni-Nb/rGO catalyst is an effective strategy to not only boost the sorption kinetics of MgH2 but also maintain its cycling property.
基金项目
National Natural Science Foundation of China(51801078)
NETL
NSTL
万方数据