For the films with 13% and 21% Cu (c and e), the dealloying procedure decreased the copper

content in the film and resulted in surface pits where copper was removed (d and f). The pits formed in the sample with the smaller initial Cu concentration (d) are smaller than those formed in the sample with the larger initial Cu concentration (f). This can be seen more clearly in the higher resolution SEM images of the post-dealloyed films in Figure 4. Figure 3 SEM images of NiCu films before (a, c, e) and after (b, d, f) the dealloying procedure. The initial copper content in the films are (a) 9.0±0.5%, AZD5582 molecular weight (c) 12.6±0.6%, and (e) 21.4±1.1%. The copper content in the dealloyed films are (b) 9.5±0.5%, (d) 11.4±0.6%, and (f) 13.9±0.7%. The scale bar is 5 μm for all the images. Figure 4 Higher resolution SEM images of the dealloyed NiCu films in (a) Figure 3 d find more and (b) Figure 3 f. The scale bar is 1 μm for both images. To compare the resulting electrochemically accessible surface areas of the samples, the electrochemical double-layer capacitance was measured for each sample both before and after

the dealloying step. In the simplest model, this capacitance is proportional to the surface area of the sample accessible via electrochemistry and thus provides a semi-quantitative measure of that area. Figure 5 shows the ratio of the measured capacitance after the dealloying step to before the dealloying step as a function of the amount of copper selectively removed. In the figure, negative Cu removed indicates that Ni was

selectively removed in the dealloying step; for these samples, when the uncertainties are taken into account, the Cu removed amounts are statistically equivalent to zero. The dashed line indicates identical measured capacitances before and after dealloying. Figure 5 Ratio of measured capacitance after to before the dealloying step. The capacitance ratio as a function of the copper composition (at.%) removed in the dealloying step. Negative Cu removed indicates that Ni was selectively removed in the dealloying step rather than Cu. The dashed line indicates identical measured capacitances before and after Tolmetin dealloying. For all the samples studied, the capacitance either stayed statistically the same or increased, suggesting that the dealloying procedure either did not change the effective surface area of the sample or caused it to increase. For the samples with between 3% and 15% Cu removed, the capacitance ratio decreases as the amount of copper removed increases. This observation is consistent with the SEM images in Figures 3 and 4. The samples with larger initial copper content tended to have rougher initial topography, such as that in Figure 3e, and thus had higher initial capacitance measurements. In addition, those samples tended to have larger pits seen in the post-dealloy topography, such as in Figure 3f, which increased the measured capacitance only modestly.