Hydrogen storage in proton-conductive perovskite-type oxides and their application to nickel–hydrogen batteries

In order to obtain a new anode material of hydrogen battery, perovskite-type oxide powders were prepared by a conventional solid-state reaction method and a subsequent mechanical milling using a planetary ball-milling machine. Hydrogen charge and discharge properties were investigated electrochemically in a three-electrode cell with KOH solution. As a result, the sample shown by ACe1−xMxO3−δ (A=Sr or Ba, M=rare earth element) was found to store hydrogen in the bulk and repeat hydrogen charge and discharge at room temperature, which suggested that the oxides are candidates for anode materials of hydrogen batteries. The maximum content of hydrogen stored was 119 mA h g−1 for BaCe0.95Nd0.05O3−δ, which corresponded to the fact that 1.44 hydrogen atoms were present in one formula of the sample. However, the cycleability was degraded with increasing the cycle number. Considering higher hydrogen-storage performance in the cerium-containing perovskite-type oxides than in the others, the valence change in cerium would have an important role to store hydrogen. Furthermore, the fact that the 1.44 hydrogens stored exceed the number of cerium in the formula suggested the presence of atomic hydrogen in the perovskite-type oxide like in the hydrogen storage alloys.