Hydrogen storage performances and reaction mechanism of non-stoichiometric compound Li_1.3Na_1.7AlH₆ doped with Ti₃C₂

Our previous work found that Li_1.3Na_1.7AlH₆ possesses the lowest dehydrogenation onset temperature and the most favorable dehydrogenation thermal stability among Li-Na-Al-H compounds (Fan et al., 2017). In this work, additional Ti₃C₂ was introduced into Li_1.3Na_1.7AlH₆ by ball milling to further enhance its dehydrogenation performances. According to the volumetric release curves, the initial dehydrogenation temperature of the sample Li_1.3Na_1.7AlH₆ + 5 wt.%Ti₃C₂ was lowered by 35 K from that of the pristine Li_1.3Na_1.7AlH₆. The dehydrogenation enthalpy values of Li_1.3Na_1.7AlH₆ + 5 wt.%Ti₃C₂ (46.9 KJ mol H₂ ⁻¹) was also slightly lower than that of pristine Li_1.3Na_1.7AlH₆ (49.7 KJ mol H₂ ⁻¹). It means that the doped Ti₃C₂ was actively involved in the reaction with Li_1.3Na_1.7AlH₆ during the dehydrogenation process. The investigation by X-ray photoelectron spectroscopy (XPS) demonstrated that the reaction between Ti element and Li_1.3Na_1.7AlH₆ was definitely carried out in which the zero valence of Ti was transformed into Ti³⁺.