Enhanced the hydrogen storage properties and reaction mechanisms of 4MgH 2 + LiAlH 4 composite system by addition with TiO 2

Abstract

A ball milling technique was used to prepare a 4MgH2-LiAlH4 doped TiO2 sample. The hydrogen storage behaviour of the system 4MgH2-LiAlH4-TiO2 and the role played by TiO2 have been systematically investigated. The result shows the decrement of the initial decomposition temperature from the 4MgH2-LiAlH4-TiO2 composite when contrasted with the 4MgH2-LiAlH4 system. The initial dehydrogenation temperature of 4MgH2-LiAlH4-10 wt% TiO2 destabilized system decreased from 100°C and 270°C of undoped composite to 70°C and 200°C, respectively, for the desorption process in the first two stages. It was also found that the re/dehydrogenation kinetics performances of the 4MgH2-LiAlH4-10 wt% TiO2 destabilized system was improved when contrasted with the non-catalyzed sample. On the other hand, the activation energy for the MgH2-relevant decomposition is reduced from 133.3 kJ/mol (4MgH2-LiAlH4 sample) to 102.5 kJ/mol (4MgH2-LiAlH4-TiO2 sample). In addition, this synergistic effect of TiO2 on the improvement of the absorption/desorption performances was related to the formation of Al3Ti and TiH2 phases in the doped sample upon desorption, which reinforces the interaction of MgH2 with LiAlH4. This further changes the thermodynamics of the reactions by modifying the absorption/desorption pathway. In conclusion, the TiO2 catalyst showed a good catalytic impact in ameliorating the hydrogen sorption behaviour of the 4MgH2-LiAlH4 sample.