Co-effects of Tm2O3 and porous silica on reversible hydrogen storage in NaAlH4

The co-effects of lanthanide oxide Tm2O3 and porous silica on the hydrogen storage properties of sodium alanate are investigated. NaAlH4–Tm2O3 (10 wt%) and NaAlH4–Tm2O3 (10 wt%)-porous SiO2 (10 wt%) are prepared by the ball milling method, and their hydrogen desorption/re-absorption capacities are compared. Dehydrogenation process was performed at 150 °C under vacuum and rehydrogenation was performed at 150 °C for 4 h under ∼9 MPa in highly pure hydrogen. The results show that Tm2O3 has a catalytic effect on the hydrogen desorption and re-absorption of NaAlH4. The hydrogen desorption capacity of Tm2O3 single-doped NaAlH4 is 4.6 wt%, higher than that of undoped NaAlH4 (4.3 wt%). During the dehydrogenation process, NaAlH4 is completely decomposed and no intermediate product Na3AlH6 is detected. The addition of porous silica improves the dehydrogenation performance of NaAlH4. Tm2O3 and porous silica co-doped NaAlH4 could release a maximum hydrogen amount of 4.7 wt%, higher than that of undoped NaAlH4 and Tm2O3 single-doped NaAlH4. Moreover, porous silica improves the reversibility of hydrogen storage in NaAlH4.