Constant-potential and constant-current discharge techniques were used to determine H diffusion coefficients in an electrode that was made of this alloy. The constant H surface concentration condition which was necessary in order to satisfy Crankâs equation was established only when the discharge potential was anodic enough to cause the H, which diffused from the bulk to the surface, to be instantly oxidized. In order to satisfy this condition, the electrode was discharged at a constant anodic potential of -0.3V. A linear relationship was found to exist between elapsed time and the logarithm of the current, at long times. From the slope of the linear portion of the above curve, the H diffusion parameter was found. The results which were obtained using the 2 discharge methods were 7 x 10-11 for constant-potential and 3.30 x 10-11cm2/s for constant-current.
Electrochemical Determination of the Diffusion Coefficient of Hydrogen through an LaNi4.25Al0.75 Electrode in Alkaline Aqueous Solution. G.Zheng, B.N.Popov, R.E.White: Journal of the Electrochemical Society, 1995, 142[8], 2695-8
Table 112
Diffusion of H in Ni3Ce-20wt%PTFE
H (g-ion/cm3) | Temperature (C) | D (cm2/s) |
0.006 | 20 | 5.2 x 10-8 |
0.006 | 40 | 5.6 x 10-8 |
0.006 | 60 | 6.9 x 10-8 |
0.013 | 20 | 2.7 x 10-8 |
0.013 | 40 | 5.2 x 10-8 |
0.013 | 60 | 4.7 x 10-8 |
0.019 | 20 | 1.5 x 10-8 |
0.019 | 40 | 4.9 x 10-8 |
0.019 | 60 | 4.2 x 10-8 |