The transport of H through amorphous or crystalline films was studied. By comparing cyclic voltammograms and electrochemical impedance spectra for the 2 types of film, it was found that the H ion absorption resistance of the crystalline film was much larger than that of the amorphous film. It was suggested that the differing behaviors of the films during measurement resulted from the open-structured nature of the amorphous films. These contained H2O, whereas the crystalline films did not. The chemical diffusivity of H ions in the amorphous films was determined as a function of the applied cathodic potential by analyzing electrochemical impedance spectra. As the applied cathodic potential was decreased from -0.45 to -0.8VSCE, the H chemical diffusivity in the amorphous films increased from about 10-10 to 10-9cm2/s. The applied potential dependence of the chemical diffusivity of the H ions was explained in terms of the interaction between H ions and lattice O ions, hydroxide ions or water. A 2-stage variation in the potentiostatic current decay transients suggested the existence of H trapping sites with a relatively high binding energy.

S.I.Pyun, D.J.Kim, J.S.Bae: Journal of Alloys and Compounds, 1996, 244[1-2], 16-22