Determination of hydrogen absorption isotherm and diffusion coefficient in Pd81Pt19 alloy

In the present paper, hydrogen absorption into Pd81Pt19 foil was studied using the permeation and impedance techniques. Pd81Pt19 is an interesting alloy in which the α-phase is extended to high hydrogen concentrations. The total amount of hydrogen absorbed is smaller than that in pure palladium and the absorption plateau is obtained at negative overpotentials. An important error in the absorbed hydrogen amount can be made if the measurements are performed in a stagnant solution because of the dissolved hydrogen formation; its charge adds to the absorbed hydrogen oxidation charge.The hydrogen diffusion coefficient was determined by various permeation and impedance techniques. They gave similar values with the exception of the small differential step permeation technique and EIS in the transmissive mode. Hydrogen induced stress might be at origin of the deviations observed in the permeation studies.