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

Abstract A two-dimensional Nb 4 C 3 T x (MXene) prepared via a chemical exfoliation was applied into MgH 2 by ball milling. The activated MgH 2 -5 wt%Nb 4 C 3 T x composite exhibits superior hydrogen storage kinetics properties. The onset temperature for the activated MgH 2 -5 wt%Nb 4 C 3 T x composite is significantly reduced from 296.5 °C (the balled pure MgH 2 ) to 150.6 °C, representing a 145.9 °C reduction, and which can release completely within 800 s at 250 °C, with a larger rate constant of 1.09164 wt% min −1 . Additionally, the apparent activation energy for dehydrogenation of the activated MgH 2 - 5wt%Nb 4 C 3 T x 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 °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 Nb 4 C 3 T x towards the hydrogen storage reaction of MgH 2 , which are likely due to the unique layered structure and in situ formed NbH x . This research extends the knowledge of designing efficient catalyst via the two-dimensional MXene in the hydrogen storage materials.