Highly-dispersed nano-TiB2 derived from the two-dimensional Ti3CN MXene for tailoring the kinetics and reversibility of the Li-Mg-B-H hydrogen storage material

Li–Mg–B–H composite (2LiBH4 + MgH2) possesses a very high hydrogen storage capacity of 11.4 wt%. However, it still suffers from high operating temperature, slow kinetics, and poor reversibility. In this work, the two-dimensional Ti3CN MXene was first synthesized and then introduced into the Li–Mg–B–H composite. The addition of 5 wt% Ti3CN reduces the onset dehydrogenation temperature of the 2LiBH4 + MgH2 composite by about 50 °C and shortens the induction period of the LiBH4 decomposition at 400 °C from >90 min to <10 min. The reversible capacity maintains at 8.3 wt% after 20 cycles, with a capacity retention ratio of 93%. Microstructure studies show that Ti3CN will partially transform to a highly-dispersed nano-TiB2 with particle size around 5 nm. Such nano-TiB2 could serve as an active catalyst to significantly improve the kinetics and reversibility of the Li–Mg–B–H composite. This work offers a strategy to enhancing the hydrogen storage performance of the advanced metal borohydride-based composites by addition of the MXene material and provides some new insights in understanding the role of MXene in tailoring the hydrogen storage properties of the Li–Mg–B–H composite.