N-doped carbon coated Ti3C2 MXene as a high-efficiency catalyst for improving hydrogen storage kinetics and stability of NaAlH4

The synthesis of highly stable catalysts for the de/hydriding kinetics and cycle stability of NaAlH4 is crucial. Herein, N-doped carbon coated two-dimensional layered Ti3C2 (Ti3C2/NC) catalyst was synthesized by a self-polymerization and heat-treatment method. Impressively, the Ti3C2/NC catalyst remarkably improves the dehydrogenation properties of NaAlH4 with dramatically enhanced dehydrogenation kinetics and stability. In detail, after adding 10 wt% Ti3C2/NC, the initial dehydrogenation temperature is lowered to 85 °C, 3.0 wt% hydrogen is liberated within 4 min at 140 °C, the first step of hydrogen desorption is completed in 57 min at 100 °C, and its capacity retention after 15 cycle tests can remain up to 96.3%. It can be found that in-situ formed Ti-species (Ti0 and Ti3+) during ball milling and the interaction between pyridinic-N and Ti0 are responsible for the enhanced hydrogen storage performance of NaAlH4. Moreover, the carbon can efficiently stabilize Ti species and results in high stability. This finding provides a new understanding of Ti-based MXene to catalyze the hydrogen storage for NaAlH4.