Mg based hydride electrodes in alkaline solution were protected by coating them with hydrogen-permeable NAFION membranes. The electrodes were fabricated by using Mg based hydrides synthesized by hydriding combustion (HC) technique. The hydriding combustion synthesized (HCSed) powders were further ball-milled and fabricated into pellet-type electrodes with and without NAFION coating. The ball-milled HCSed powder showed nearly three times higher surface area (∼15 m2 g−1) than that of the as-HC synthesized powder, and thus provided higher discharge capacity. Furthermore, the ball-milled HCSed electrode with NAFION coating exhibited nearly 400% higher discharge capacity (713 mAh g−1) than that of the un-coated as-HCSed electrode.

Superiority of the hydriding combustion (HC) technique over conventional metallurgical approach to the synthesis of cost-effective Mg based hydrides, which show promise as hydrogen storage materials, is well known. In the present research, we report further improvements in HC prepared Mg-based materials, achieved by optimizing the preparative parameters of HC and by catalytic addition. Mg90-Ni60-C40 composites prepared using optimized processing parameters were ball-milled with NbF5 (10 h) and characterized for their micro-structural and hydriding properties. The ball-milled/catalyzed powder showed decreased crystallinity with CNTs on its surfaces. Surface area of the ball-milled powder decreased to almost half of the as-HC powder, while TG analysis revealed a four-fold decrease in the desorption temperature of the milled powder compared to that of the as-HC prepared powder. Activated samples achieved the maximum absorption/desorption limits (5.3 wt.%) at as low as 100°C, underlining the possibility of the use of these materials in portable hydrogen storage devices.

Magnesium may be the most promising solid-state hydrogen storage material owing to its high storage capacity (7.6 wt%) and highest volumetric density (2 times of liquid H2). On the other hand, suffers from its sluggish absorption/desorption characteristics. In the present study, the simple/cost-effective hydriding combustion synthesis (HCS) was used to prepare highly-active Mg-based-samples. The preparative parameters of HCS were varied, and its effects on the micro-structural and hydrogen storage properties were determined. The results and its analysis showed that the simple HCS process possesses a multifaceted dependence on a range of experimental factors and affect the final product. The estimated dependence enabled us to explain the combined effect of individual experimental factors on the prepared samples. The Mg–Ni–C sample prepared at 610 °C with 6%wt-nano-Ni and 4 wt%-multi-walled-CNTs as reactants, resulted in sample with a surface area as high as 19.01 m2/g and a desorption capacity of 5.77 wt%, highlighting the promising characteristics of HCS to prepare highly-active Mg-based-materials.

This study employed a fast, simple and cost-effective hydriding combustion synthesis (HCS) to prepare nano/submicron Mg based alloys, which are the most promising solid state hydrogen storage materials owing to their high storage capacity (7.6 wt.%) and highest volumetric density. The microstructural and absorption/desorption kinetic properties of the prepared MgH2 samples were characterized and compared with commercially available MgH2 powders. The detailed BET analysis of the HCS prepared samples showed a higher surface area than that of commercial MgH2, which resulted in better absorption/desorption kinetics. The HCS-prepared MgH2 powder absorbed 6.2 wt.% H2 with a rate of 0.31 wt.%/min, whereas it desorbed at a rate of 0.98 wt.%/min. These results highlight the superiority of the HCS method to prepare MgH2 powders over conventional ingot-metallurgy.