Mohammad Ismail

The imperative for renewable energy transition hinges on the development of efficient storage solutions, with hydrogen storage being a frontrunner due to its high energy yield and clean combustion profile. This study explores the enhancement of hydrogen storage properties via Iron (III) chloride (FeCl3) doping into a 2NaAlH4 + Ca(BH4)2 composite. Through six-hour ball milling process, the transformation of NaAlH4 and Ca(BH4)2 into Ca(AlH4)2 and NaBH4 phases is achieved, setting a benchmark for subsequent analyses. We have delineated four principal dehydrogenation stages where FeCl3 doping has substantially lowered the decomposition temperatures, as indicated by the onset of hydrogen release at 100 °C in the doped composite—a reduction from the 125 °C observed in the undoped material. These findings are substantiated by Differential Scanning Calorimetry (DSC) which confirms the lower temperature thresholds across all dehydrogenation stages, while Scanning Electron Microscopy (SEM) illustrates a uniform distribution of smaller, finer particles in the doped composite, suggesting an increased surface area that potentially enhances kinetic rates due to shorter diffusion paths for hydrogen. The insights from this research not only illuminate the effectiveness of FeCl3 as a dopant in improving hydrogen storage capabilities but also highlight the broader implications of such materials in enhancing the practicality and efficiency of hydrogen as a renewable energy vector, thereby contributing to the collective efforts in overcoming the challenges of hydrogen storage.

As a hydrogen storage material, both AlH ₃ and LiNH ₂ possess a high hydrogen capacity. However, the dehydrogenated AlH ₃ can hardly absorb hydrogen under normal conditions, while LiNH ₂ will generate NH ₃ rather than H ₂ upon decomposition. In this work, we report that the combination of AlH ₃ and LiNH ₂ through simple ball milling leads to partial reversibility of the AlH ₃ −LiNH ₂ system and the suppression of NH ₃ liberation. The negatively charged H ^{δ −} in AlH ₃ will react with the positively charged H ^{δ +} in LiNH ₂ through a redox reaction to form Li ₂ NH, AlN, and H ₂ at 120−170 °C. After dehydrogenation at above 270 °C, Li ₃ AlN ₂ is generated, which is crucial for the reversibility of this system. The more the Li ₃ AlN ₂ generated, the better the reversibility of this system. The dehydrogenation capacity of AlH ₃ + 2LiNH ₂ at the third cycle (3.0 wt%) is higher than that of AlH ₃ + LiNH ₂ (1.2 wt%) due to the generation of more Li ₃ AlN ₂ . The role of AlH ₃ /Al in the AlH ₃ −LiNH ₂ system is to fix the nitrogen into the form of AlN and Li ₃ AlN ₂ and thus suppress the liberation of NH ₃ . Therefore, the synergy of AlH ₃ and LiNH ₂ leads to the reversibility of the Li–Al–N–H system and the suppression of NH ₃ .