Hydrogen is a CO₂ free fuel and can be stored in many different forms as compressed or liquefied hydrogen in tanks. Liquid ammonia has been expected as a hydrogen carrier because it has a high H₂ storage capacity with 17.8 wt% and 10.7 kgH₂/100L at 1MPa and 298K. The volumetric hydrogen density is about 1.5 times of liquid hydrogen, and it is easily liquefied under about 1 MPa at room temperature. Current PEM fuel cells are poisoned even by trace levels (~1 ppm) of ammonia. The catalyst such as Ru supported on MgO shows the ammonia conversion of 99.8 % at 773K, which corresponds to ammonia concentration of 1000 ppm. After hydrogen and nitrogen generation by ammonia cracking, ammonium hydrogen sulfate (NH₄HSO₄) can be utilized to decrease the ammonia concentration from 1000 ppm to 0.1 ppm.