Nitrogen-modified Ti3C2 MXene with enhanced catalytic activity for efficient hydrogen storage in MgH2

Abstract

The practical implementation of MgH₂ is impeded by its slow kinetics. Herein, surface engineering of Ti₃C₂ via nitrogen doping was employed to synthesize nitrogen-doped Ti₃C₂ (N-Ti₃C₂) and improve the hydrogen storage properties of MgH₂. The results reveal that N-Ti₃C₂ prepared at 600 °C (denoted as N-Ti₃C₂-600) possesses superior catalytic performance compared to pristine Ti₃C₂. The initial hydrogen liberation temperature is reduced from 287 °C (for pure MgH₂) to 169 °C for MgH₂ with N-Ti₃C₂-600. In addition, MgH₂ + 5 wt% N-Ti₃C₂-600 can rapidly desorb 7.0 wt% H₂ in 10 min at 240 °C, and absorb 5.4 wt% H₂ in 100 min at 50 °C. Moreover, the dehydrogenation activation energy of MgH₂ doped with N-Ti₃C₂-600 is 78.90 kJ/mol, demonstrating superior kinetics. Microscopic analysis demonstrates that the uniformly distributed and stable titanium species (Ti⁰ and Ti²⁺) and nitrogen species (C=N), along with their interaction, contribute to the enhanced kinetics and cyclic stability of MgH₂. This research presents a viable approach to developing MXene-based catalysts for solid-state hydrogen storage.