Characteristics of Hydrogen Absorption-Desorption Reaction in R-M (R=Y, La, Ce; M=Co, Rh, Ir, Ni, Pd, Pt) Binary Systems

摘要

The amount of absorbed hydrogen, the absorption rate and the reversibility of hydrogen absorption-desorption reaction were measured for binary systems R-M (R= Y, La, Ce; M=Co, Rh, Ir, Ni, Pd, Pt). These experimental results were discussed by comparing the number of states unoccupied by electrons, the cohesive energy and the energy fluctuation, which were calculated by the extended Hueckel method. The main results are as follows, (a) The more the number of unoccupied electronic states in the compounds, the more hydrogen is absorbed, (b) the critical concentrations of hydrogen in the R-M compounds where the energy fluctuation decreases remarkably correspond to the inflection or saturation points in the absorption curve, and (c) when the cohesive energy of a compound decreases linearly with hydrogen concentration, the compound easily desorbs hydrogen. On the other hand, when a sharp knickpoint is observed in the curve of cohesive energy - hydrogen concentration, the desorption reaction is hard to occur.