In Situ Formed Ti/Nb Nanocatalysts within a Bimetal 3D MXene Nanostructure Realizing Long Cyclic Lifetime and Faster Kinetic Rates of MgH2.

Abstract

Magnesium hydride (MGH) is a high-capacity and low-cost hydrogen storage material; however, slow kinetic rates, high dehydrogenation temperature, and short cycle life hindered its large-scale applications. We proposed a strategy of designing novel delaminated 3D bimetal MXene (d-TiNbCTx) nanostructure to solve these problems. The on-set dehydrogenation temperature of MGH@d-TiNbCTx composition was reduced to 150 °C, achieving 7.2 wt % of hydrogen releasing capacity within the range of 150-250 °C. This composition absorbed 7.2 wt % hydrogen within 5 min at 200 °C and 5.5 wt % at 30 °C within 2 h, while the desorption capacity (6.0 wt %) was measured at 275 °C within 7 min. After 150 cycles at 250 °C, the 6.5 wt % capacity was retained with negligible loss of hydrogen content. These results were attributed to the catalytic effect of in situ-formed TiH2/NbH2 nanocatalysts, which lead to dissociate the Mg-H bonds and promote of kinetic rates. This unique structure paves great opportunities for designing of highly efficient MGHs/MXene nanocomposites to improve the hydrogen storage performance of MGHs.