Preparation of Li-Mg-N-H hydrogen storage materials for an auxiliary power unit

Solid hydrogen storage materials as H2 supply for PEM fuel cells have been attempted over the past decades because of their high efficiencies in H2 storage. However, most investigations were focused on the stage of tank design for the storage materials. The Li-Mg-N-H hydrogen storage system was for the first time integrated into a HT-PEM fuel cell stack for a prototype auxiliary power unit, the maximum working temperature being 200 °C. With a designed output of 1 kW, a few kilograms of storage materials are needed. By using commercially available raw materials, an up-scaled preparation of the storage material was performed using laboratory facilities. Preparation conditions were established with the aid of FTIR, TG-DSC and x-ray diffraction to ensure the desired quality of materials. Prior to power the fuel cell stack, the storage materials need to go through an exothermic metathesis, and severe temperature overshooting is expected, which may cause deterioration in material performance and safety issue. Operation conditions were tested and the temperature overshooting could be effectively prevented under adequate conditions.