Preparation, characterization and modification of magnesium hydride for enhanced solid-state hydrogen storage properties

• Published in: International journal of hydrogen energy 2024-12, Vol.96, p.494-501
• Main Authors: Paul, Bhaskar, Kumar, Sanjay, Majumdar, Sanjib
• Format: Article
• Language: English
• Subjects: Hydrogenation-dehydrogenation; Hydrolysis of hydride; Magnesium hydride; TGA
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2024.11.340

Magnesium–magnesium hydride (Mg–MgH2) system has attracted attention worldwide recently because of its simple hydrogenation-dehydrogenation process, the cost-effectiveness of the raw materials, and relatively high hydrogen storage capacity compared to the other metal-metal hydride systems. The present study deals with the optimization of the process parameters for the synthesis of magnesium hydride (MgH2) in sizable quantities using commercial-grade magnesium powder, characterization with respect to hydrogen storage capacity, by thermal dehydrogenation and pH-controlled aqueous hydrolysis. The thermal hydrogenation-dehydrogenation and mild acidified aqueous dehydrogenation behaviour of MgH2 were studied systematically to compare the decomposition kinetics and storage capacity. The superior catalytic effect of V2O5 on decreasing the onset-dehydrogenation temperature of MgH2 is demonstrated. The MgH2-5 wt. % mesoporous V2O5 sample starts releasing hydrogen at 220 °C, which is substantially less than the as-synthesized un-catalysed MgH2 under identical conditions which starts releasing hydrogen at 430 °C. The dehydrogenated MgH2-5wt. %V2O5 could be completely re-hydrogenated at 150 °C. Hydrolysis of as-synthesized MgH2 was demonstrated using an aqueous solution using tartaric acid and the dehydrogenation behaviour was co-related with the pH of the solution. More than 90% hydrogen yield was achieved by the hydrolysis of MgH2 in a tartaric acid solution of pH-4. Based on the result, a hydrogen gas dispenser using solid-state magnesium hydride as a hydrogen source is proposed for laboratory applications for the supply of ultra-pure hydrogen for various reactions and crystal growth experiments. •MgH2 was successfully synthesized from Mg powder.•Hydrogenation - dehydrogenation kinetics was improved by catalysis.•Onset of desorption temperature decreased by 175 °C.•Absorption of >6 wt % of H2 in less than 1h at 150 °C.•More than 90% hydrogen yield by hydrolysis of MgH2 achieved by using tartaric acid.