Thermodynamics and kinetics of hydrogen/deuterium absorption-desorption in Pd0.77Ag0.23 alloy

Pd0.77Ag0.23 alloy foil of thickness ∼100 μm was prepared by arc melting followed by cold rolling and annealing. The X-ray diffraction pattern confirmed the formation of solid solution phase and the TXRF analysis confirmed the composition as Pd0.77Ag0.23. Hydrogen/deuterium equilibrium pressure-composition-temperature (PCT) relationships for this alloy were experimentally generated over the temperature range of 374-419 K using Sieverts' type volumetric apparatus. Thermodynamic parameters like enthalpy and entropy of hydrogen/deuterium desorption reaction were evaluated from PCT data. Kinetics of hydrogen/deuterium absorption for this thin alloy foil was also investigated in the temperature range of 335-394 K using the same apparatus and activation energies of hydrogen/deuterium absorption reactions were evaluated. Both thermodynamic and kinetic data showed pronounced positive isotope effect in the temperature and pressure range of investigation.