Improved hydrogen storage performance of magnesium hydride catalyzed by two dimensional Ti3C2-coated NbN

Abstract

With rising energy demand for energy and the deterioration of the environment, the search for finding a sustainable energy material is crucial. Hydrogen energy has been widely recognized as a clean energy source, and magnesium-based hydrogen storage material (MgH₂) is a material with great potential, but some of its properties limit its practical application. In this study, we prepared flower-shaped niobium nitride (NbN) and 2D titanium carbide (Ti₃C₂). Subsequently, the two materials were compounded to yield a NbN@Ti₃C₂ composite material. Because of the synergistic effect of NbN and multivalent Ti as a catalytic pair, the addition of 7 wt% NbN@Ti₃C₂ significantly reduced the dehydrogenation temperature of MgH₂ from 305 °C to 185 °C. Under isothermal dehydrogenation at 300 °C, 5.9 wt% of H₂ was dissociated within 180 s. The dehydrogenation activation energy was measured to be 44.82 ± 2.57 kJ/mol, considerably lower than that of ball-milled MgH₂ (126.04 ± 3.65 kJ/mol), representing a relative reduction of 64.4 %. The presence of carbon effectively avoids the reunification phenomenon during the cyclic testing; thus, the MgH₂-7 wt% NbN@Ti₃C₂ composite material maintained an effective H₂ capacity of approximately 95.5 % after 50 cycles at 300 °C, substantially enhancing the cyclic stability of MgH₂.