Thermodynamic properties of hydrogen in fine Pd powders

Abstract

Abstract The effect of Pd particle size on the thermodynamic properties of the Pd–H system was examined at 298 to 373 K. In this study, the pressure–composition(PC) isotherms were determined for Pd fine powders with around 0.2 μm in diameter of primary particle and derived thermodynamic properties were compared with values obtained for Pd sheet. In the solid solution region, the hydrogen solubility increased with reducing Pd particle size. This is similar to the case found for LaNi 5 –H system. On the other hand, it was found that the plateau pressures on P–C isotherms increased with decreasing particle size at relatively low temperatures, which is the reverse to the case for LaNi 5 –H system. This research demonstrates the difference in thermodynamic properties of hydrogen in between fine Pd powders and Pd sheet, well reflecting the difference in hydrogen solubility and plateau pressure on PC isotherms.