2LiBH4MgH2 in a ResorcinolFurfural Carbon Aerogel Scaffold for Reversible Hydrogen Storage

Abstract

The reactive hydride composite of 2LiBH4–MgH2 has been melt infiltrated in a resorcinol–furfural (RFF) carbon aerogel scaffold. Dried aerogel of RFF, further pyrolyzed to obtain a carbon aerogel scaffold, is prepared by CO2 supercritical drying, where time consumption is significantly lower than the normal procedures of solvent exchange and drying under ambient conditions. On the basis of scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) mapping, the complex hydrides are homogeneously dispersed in the nanometer scale both inside the nanopores and over the surface of the RFF carbon aerogel. Synchrotron radiation powder X-ray diffraction (SR–PXD) and Raman results reveal the reaction mechanisms during melt infiltration, de- and rehydrogenation of this system, as well as the differences from the previous studies of the nanoconfined 2LiBH4–MgH2 in a resorcinol–formaldehyde (RF) carbon aerogel. Thermogravimetric and hydrogen titration measurements reveal a significant improvement in dehydrogenation kinetics of 2LiBH4–MgH2–RFF as compared with the bulk 2LiBH4–MgH2 system. For instance, an approximate single-step dehydrogenation together with almost 100% of the total hydrogen storage capacity is accomplished within 6 h during the first dehydrogenation, while the bulk material performs clearly two-step reaction and requires 30 h (at T = 45 °C and p(H2) = 3–4 bar). Moreover, the gravimetric hydrogen storage capacity in the range of 4.2–4.8 wt % (10–11.2 wt % H2 with respect to the hydride content) is maintained over four dehydrogenation and rehydrogenation cycles.