Thermally induced in situ fabrication of TiO2/CN heterojunction dopant for enhancement of hydrogen storage properties of LiAlH4

Abstract

Herein, a novel TiO2/CN heterojunction material has been prepared by one-step bubble template-assisted calcination to enhance the hydrogen storage capability of LiAlH4. The TEM, XPS and UPS analysis confirm that a heterostructure is formed between TiO2 and g-C3N4 successfully. The experimental findings indicate that the TiO2/CN significantly enhances the dehydrogenation performance of LiAlH4. For instance, the LiAlH4-7 wt% TiO2/CN starts to dehydrogenize at 76 °C (94 °C less than pure LiAlH4) and releases 6.5 wt% H2 at 200 °C. Meanwhile, LiAlH4-7 wt% TiO2/CN releases 4.9 wt% H2 at 120 °C within 50 min. The mechanism analysis illustrates that AlTi3N is formed in situ during ball-milling. And density functional theory (DFT) calculation results reveal that the AlTi3N can weaken the Al-H bonds in LiAlH4 through interfacial charge transfer. Furthermore, the TiO2/CN heterostructure creates an internal electric field that generates an electron-rich layer. As a result, the negative electron layer at one end of the TiO2/CN heterojunction has an increased affinity for H, which enhances the dehydrogenation reaction of LiAlH4. Clearly, both the TiO2/CN heterostructure and AlTi3N contribute to the improvement of the dehydrogenation properties of LiAlH4.