Hydrogen Sorption Improvement of LiAlH4 Catalyzed by Nb2O5 and Cr2O3 Nanoparticles

Abstract

The use of LiAlH4 as a promising hydrogen storage material is limited by its high desorption temperature, slow kinetics, and poor reversibility. In the present work, the influence of the catalytic activity of Nb2O5 and Cr2O3 nanoparticles on the hydrogen sorption properties of LiAlH4 was investigated. It was shown that Nb2O5 was superior to Cr2O3 in improving the dehydriding property. For instance, samples of LiAlH4 doped with 1 and 2 mol % Nb2O5 showed improvement in the onset desorption temperature with little decrease in hydrogen capacity, where approximately 6.9 wt % was released by 193 °C. Isothermal desorption results at 120 °C revealed that enhancements arising upon adding Nb2O5 were almost 6–7 times that of pristine LiAlH4. Moreover, LiAlH4–2 mol % Nb2O5 displayed a substantially reduced activation energy and enthalpy change for LiAlH4 dehydrogenation. The results of the first rehydrogenation indicated that the amount of restored hydrogen for Nb2O5-doped samples was lower than that of samples with Cr2O3. XRD, FESEM-EDS, and XPS examinations suggested that finely dispersed Nb species with a range of valence states might contribute to the kinetic improvement by serving as active sites for nucleation and growth of dehydrogenated product.