Systematic investigation of hydrogen storage properties in RNi5-H (R = rare earth) systems

Abstract

We investigated hydrogen storage properties in RNi5-H (R = rare earth) systems. Pressure-composition isotherms showed that a single pressure plateau separates into two plateaus (lower and higher plateau) as the atomic number of Relement in RNi5-H systems increases, indicating the presence of two hydrides. In higher-number RNi5-H systems, both plateaus disappear, while another pressure plateau related to a novel hydride appears at low hydrogen content. The decrease of the unit cell volume due to the lanthanide contraction leads to the instability of hydrogen, suggesting an increase in both the lower and higher plateau pressures.