Absorption/desorption of deuterium at Pd95% - Rh5% alloy. Part 1: environment and temperature effects

The gas phase and electrolytic loading of Pd95%-Rh5% alloy with deuterium were investigated. Gas loading was carried out isochorically under 900 mbar D2, by decreasing the temperature from 900 °C to 20 °C. Although some D 2 was absorbed from high temperatures downwards, most of the absorption was measured at 20 °C, at which the [D]/[Me] (deuterium to metal atom) ratio exceeded the value typical for pure Pd. When the alloy deuterides were heated from 20 °C to 900 °C, they where found to decompose for temperatures below 100 °C, but some deuterium was still absorbed at high temperatures. The electrolytic insertion of deuterium was carried out potentiostatically in alkaline D20 electrolytes, the amount of deuterium loaded being determined by anodic extraction afterwards. The maximum [D]/[Me] ratios thus achieved at 25 °C, which exceeded those obtained by gas loading, were found to increase with the alkalinity of the electrolyte. With electrolytic insertion at 90 °C, alloy deuterides of large [D]/[Me] ratio could be obtained which, in the electrolytic environment, showed a thermal decomposition rate much slower than that tested in gas phase desorption experiments.