In-Situ Synthesis of Nb 2 O 5 -NbC Heterojunctionsregulates the Hydrogen Storage Performance of MgH 2

Abstract

Among diverse hydrogen storage materials, magnesium hydride (MgH 2 ) is a promising solid-state candidate featuring high hydrogen capacity and low cost. However, its sluggish dehydrogenation kinetics and high initial dehydrogenation temperature drastically limit the large-scale commercialization and practical application of MgH 2 . This work focuses on breaking the dehydrogenation kinetic barrier via designing a unique heterostructure catalyst to reduce desorption temperature and improve hydrogen storage performance. Ultrafine Nb 2 O 5 -NbC heterojunctions evenly dispersed in carbon nanofiber (CNF) matrix were synthesized through a simple electrospinning method, where polystyrene (PS) acted as a growth regulator to prevent nanoparticle agglomeration. Experimental and theoretical results demonstrate that higher electrospinning speed enlarges CNF diameter, lowering Nb 2 O 5 -NbC heterojunction density per unit matrix and increasing the initial desorption temperature of MgH 2 composite. Relative to neat ball-milled MgH 2 , the MgH 2 composite modified by Nb 2 O 5 -NbC/CNF-PS catalyst shows 52.6˚C decline in initial dehydrogenation temperature and 29.1˚C drop in peak desorption temperature. The enhanced dehydrogenation performance is mainly attributed to the synergistic catalysis of Nb 2 O 5 -NbC heterojunctions. Moreover, the CNF matrix serves as a confinement scaffold to stabilize heterojunction nanoparticles and provides auxiliary catalytic activity, further elevating the overall hydrogen storage properties of MgH 2 .