The hydrogen diffusion coefficient in an LmNi3.55Co0.75Mn0.4Al0.3 alloy electrode was evaluated by potential-step method as a function of initial hydrogen concentrations in the bulk of alloy electrode (CH < 0.1 H/M) and temperature (293–333K). The hydrogen diffusion coefficient was found to decrease linearly with the increase of CH at all temperatures. However, the slope of this linear dependence was found to reduce with the increasing temperature. The partial interaction Gibbs energy of dissolved hydrogen, ΔGint, revealed a strong influence of temperature on the stability of α-solid solution phase in the alloy electrode. Namely, ΔGint gradually increased from −25.6 to −2.5kJ/mol with increasing temperature, showing a linear dependence. It was found that the Einstein diffusion coefficient of hydrogen increased also with increasing temperature, and that the apparent energy of activation of hydrogen diffusion was 27.9kJ/mol. A novel viewpoint in understanding of the hydrogen diffusion kinetic in hydrogen storage alloys was discussed in view of the thermodynamic stability of the resulting hydrides.

Hydrogen Diffusion Behavior in α-Solid Solution Phase of LmNi3.55Co0.75Mn0.4Al0.3 Metal Hydride Electrode - Effect of Temperature. N.Potkonjak, S.N.Blagojević, D.Ž.Sužnjević: Journal of Alloys and Compounds, 2009, 484[1-2], 689-92