Excellent catalytic activity of a two-dimensional Nb4C3Tx (MXene) on hydrogen storage of MgH2

A two-dimensional Nb4C3Tx (MXene) prepared via a chemical exfoliation was applied into MgH2 by ball milling. The activated MgH2-5wt%Nb4C3Tx composite exhibits superior hydrogen storage kinetics properties. The onset temperature for the activated MgH2-5wt%Nb4C3Tx composite is significantly reduced from 296.5 degrees C (the balled pure MgH2) to 150.6 degrees C, representing a 145.9 degrees C reduction, and which can release completely within 800 s at 250 degrees C, with a larger rate constant of 1.09164 wt% min(-1). Additionally, the apparent activation energy for dehydrogenation of the activated MgH2-5wt%Nb4C3Tx composite is 81.2 kJ/mol H-2 much lower than that of the balled pure Mg (153.8 kJ/mol H-2). After dehydrogenation, the sample can absorb approximately 3.50 wt% hydrogen within 2 h at temperatures as low as 50 degrees C, and the apparent activation energy for hydrogenation decreases to 27.8 kJ/mol H-2 much lower than that of the dehydrogenated pure Mg (82.1 kJ/mol H-2). Such excellent hydrogen storage kinetics and lower energy barriers explain high catalytic activity derived from Nb4C3Tx towards the hydrogen storage reaction of MgH2, which are likely due to the unique layered structure and in situ formed NbHx. This research extends the knowledge of designing efficient catalyst via the two-dimensional MXene in the hydrogen storage materials.