Unraveling the Synergistic Catalytic Effects of TiO₂ and Pr₆O₁₁ on Superior Dehydrogenation Performances of α-AlH₃

Abstract

The pivotal steps for the practical application of dehydrogenation of aluminum hydride (AlH 3 ) have been to decrease the temperature and increase the content of AlH 3 . Herein, the initial dehydrogenation temperature of AlH 3 decreased to 43 °C with the amount of released hydrogen of 8.3 wt % via introducing TiO 2 and Pr 6 O 11 with synergistic catalysis effects, and its apparent activation energy of the dehydrogenation reaction decreased to 56.1 kJ mol −1 , which is 52% lower than that of pure AlH 3 . These differences in performances of the samples are further evaluated by determining the electron density of Al−H bonds during dehydrogenation. The multiple valence state conversions of TiO 2 and Pr 6 O 11 promoted the electron transfer of H in AlH 3 , and a novel dehydrogenation pathway of PrH 2.37 formed simultaneously, which could accelerate the breakage of Al−H bonds. The density functional theory calculations further exhibit that there are fewer electrons around H in AlH 3 and the Al−H bond energy is weaker at the atomic levels, which is more conducive to the release of hydrogen. A higher hydrogen storage capacity and a lower dehydrogenation temperature make AlH 3 one of the most promising hydrogen source media for mobile applications.

Superior Dehydrogenation Performance of α‐AlH3 Catalyzed by Li3N: Realizing 8.0 wt.% Capacity at 100 °C

“…The test results of the isothermal dehydrogenation curve were consistent with the derivative curves of the above non-isothermal dehydrogenation curve (Figure 3b,f). As shown in Table 2, compared with some reported works and the previous work of our group, [32,[47][48][49][50] aluminum hydride catalyzed by lithium nitride has a faster hydrogen release rate and higher hydrogen storage capacity at low temperature, especially at the working temperature zone of the fuel cell (≈90 °C). On the other hand, at normal atmospheric ambient temperature (<50 °C), the stability of the mixture is also quite satisfactory.…”

“…[ 31 ] Our group has put forward the synergistic catalytic effects of TiO 2 and Pr 6 O 11 during the dehydrogenation process of α‐AlH 3 and results showed that the apparent activation energy and initial temperature of the dehydrogenation reaction decreased to 56.1 kJ mol −1 and 43 °C, respectively. [ 32 ] Although this work greatly developed the catalytic dehydrogenation process of aluminum hydride, there are still some shortcomings, such as the unstable self‐dehydrogenation caused by wide dehydrogenation temperature range, the slow hydrogen release rate, as well as poor capacity at a relatively lower temperature.…”

Directed Stabilization by Air-Milling and Catalyzed Decomposition by Layered Titanium Carbide Toward Low-Temperature and High-Capacity Hydrogen Storage of Aluminum Hydride

“…C–C, C–O, O–CO, and C–F bonds still exist and hardly change. In the Al 2p spectra in Figure c, the peak with binding energy of 74.2 eV corresponds to Al 2 O 3 In addition, the peak at 72.1 eV corresponding to Al is observed after decomposition, which comes from the decomposition of AlH 3 to form Al.…”

“…In the Al 2p spectra in Figure c, the peak with binding energy of 74.2 eV corresponds to Al 2 O 3 In addition, the peak at 72.1 eV corresponding to Al is observed after decomposition, which comes from the decomposition of AlH 3 to form Al. The XPS results show that Ti 3 C 2 does not change before and after decomposition, which is consistent with the XRD results in Figure .…”

“…As for the decomposition of AlH 3 , researchers have adopted some valid methods to improve the decomposition performance of AlH 3 . For instance, metals and their compounds were added as catalysts (e.g., TiF 3 , NbF 5 , Nb, CeO 2 , TiO 2 –Pr 6 O 11 , and LaNi 5 ), or composite systems (LiBH 4 –AlH 3 , , MgH 2 –AlH 3 , etc.) were built.…”