Investigation of the Ternary Mixture of Complex Hydrides for Hydrogen Storage Materials Development

Solid hydrogen storage materials have been investigated as hydrogen carriers due to their safety in hydrogen applications. In contrast, they also have some disadvantages, such as a low hydrogen capacity, very high desorption/adsorption temperature, low kinetic rate, and low reversibility. Many attempts have been made to improve and identify materials that can be applied for on-board hydrogen storage for fuel cells. This work investigates the ternary mixture of complex hydrides—LiNH₂+LiAlH₄+MgH₂—on the desorption/absorption temperature for a set of novel hydrogen storage materials. The ternary mixture is prepared by using mechanical ball-milling. In previous studies, the results from the reaction of the binary mixture 2LiNH₂+MgH₂ showed that the kinetic rate was slow and created a serious problem in NH₃ emission. The LiAlH₄ was also studied and it was reported that the kinetic barrier transformation was easily overcome by mixing it with LiNH₂ and its stability of dehydriding was also controlled. One of these reactions, Mg(NH₂)₂+2LiH ↔ Li₂Mg(NH)₂+2H₂ is known as a reversible reaction. Our study demonstrates that by starting from the ternary mixture of complex hydrides—LiNH₂+LiAlH₄+MgH₂—the kinetic rate is improved and the reversibility is maintained. Phase transformation and the amount of hydrogen desorption are analyzed by XRD and TPD measurements.

Keywords: LiNH₂, LiAlH₄, MgH₂, Hydrogen Storage, Complex Hydrides