Fabrication of Zinc-Loaded Hollow Glass Microspheres (HGMs) for hydrogen storage

Abstract: The greatest challenge for a feasible hydrogen economy lies on the production of pure hydrogen and the materials for its storage with controlled release at ambient conditions. Hydrogen with its great abundance, high energy density and clean exhaust is a promising candidate to meet the current global challenges of fossil fuel depletion and green house gases emissions. Extensive research on hollow glass microspheres (HGMs) for hydrogen storage is being carried out world-wide, but the right material for hydrogen storage is yet underway. But many other characteristics, such as the poor thermal conductivity etc. of the HGMs, restrict the hydrogen storage capacity. In this work, we have attempted to increase the thermal conductivity of HGMs by ZnO doping. The HGMs with Zn weight percentage from 0 to 10 were prepared by flame spheroidization of amber-colored glass powder impregnated with the required amount of zinc acetate. The prepared HGMs samples were characterized using field emission-scanning electron microscope (FE-SEM), environmental SEM (ESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. The deposition of ZnO on the microsphere walls was observed using FE-SEM, ESEM and HRTEM which was further confirmed using the XRD and ultraviolet–visible absorption data. The hydrogen storage studies done on these samples at 200 °C and 10-bar pressure for 5 h showed that the hydrogen storage increased when the Zn percentage in the sample increased from 0 to 2%. The percentage of zinc beyond 2, in the microspheres, showed a decline in the hydrogen storage capacity. The closure of the nanopores due to the ZnO nanocrystal deposition on the microsphere surface reduced the hydrogen storage capacity. The hydrogen storage capacity of HAZn2 was found 3.26 wt% for 10-bar pressure at 200 °C.

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