Abstract
Ultrafine theta-Al2O3 (θ-Al2O3) nanowires with average diameters of sub-10nm and lengths up to several micrometers have been successfully synthesized via a novel two-stage method. With temperature gradually elevated, θ-Al2O3 was generated from the slow transformation of gamma-phase Al2O3 (γ-Al2O3), and its ultrafine nanowire structure was formed from the recrystallization of γ-Al2O3 nanowire. By means of nitrogen adsorption–desorption isotherm at 77K and the multipoint Brunauer–Emmett–Teller (BET) method, the specific surface area of the ultrafine θ-Al2O3 nanowires is found to be up to~120m2/g. With the high surface area, the material displays excellent gas absorption ability. Hydrogen absorption capacities could be measured to be~5.57wt% at 77K (liquid nitrogen), 1.51wt% at 298K (room temperature) and 0.81wt% at 557K, when a pressure of 30atm (~3MPa) is applied. The crystal or chemical nature of metastable θ-Al2O3 phase may play a vital role in the observed excellent gas storage capacity.
•The θ-Al2O3 generated from the slow transformation of γ-Al2O3.•The ultrafine nanowire structure formed from the recrystallization of γ-Al2O3 nanowire.•The nanowires possess average diameters of sub-10nm and lengths up to several micrometers.•Their Brunauer–Emmett–Teller (BET) specific surface area was measured to be~120m2/g.•Hydrogen uptake capacity is up to 5.57wt% at 77K, 1.51wt% at 298K and 0.81wt% at 557K, respectively.