Figure (b) presents the plot of the fitted PDW parameters as a function of electrode potentials. Although D 1 is generally one order of magnitude higher than D 2 , D 1 and D 2 vary similarly across different electrode potentials. The faster diffusion coefficient, D 1 , is attributed to grain boundary diffusion, while D 2 is attributed to lattice diffusion. The coverage θ and 1 -θ are associated with D 1 and D 2 , respectively, showing that the grain boundary diffusion plays a major role at every potential. Similarly to the diffusion coefficients, the coverage values also vary with electrode potentials. Further dedicated investigations, coupled with other characterization techniques, are needed to fully understand the changes in D 1 , D 2 , and θ as a function of electrode potentials.