Thermodynamics and stability of dissolved hydrogen in pd rich binary Pd<inf>1-x</inf>Z<inf>x</inf> and ternary Pd<inf>1-x-y</inf>Z<inf>x</inf>Z<inf>y</inf>′ solid solution alloys

The relative chemical potential of the dissolved hydrogen (Δμ0H) and the partial pair interaction free energies, gPH↔Z, and (gPH↔Z/Z)average respectively, in Pd based Pd1 - xZx-H and Pd1 - x - yZxZ′y-H systems are correlated to the stability of the dissolved hydrogen in the octahedral interstitial sites by classifying the Pd1 - xZx alloys based on the "effective valence, ns" of the substitutional metals. From the dependence of Δμ0H on the lattice constant of the alloy, (a0)alloy, and of gPH↔Z ((gPH↔Z/Z′)average) on the ionic diameter of the substituent metal, dZ, ((dZ/Z′)average) for systems Pd1 - xZx-H (Pd1 - x - yZxZ′y-H), the exceptional behavior of the binary "expanded" alloys Pd1 - xZx (Z = Nb, Ta and Pt), the binary "contracted" Pd1 - xZx alloys (Z = Ti and Li) and the ternary "contracted" alloys Pd0.903Er0.078Cu0.019 and Pd1 - 2xAgxNix towards hydrogen absorption is explained. © 1998 International Association for Hydrogen Energy.