Differential capacity vs. electrode potentialcurves for Fe-HClO 4 in the presence of organic anions

Abstract

The influence of acetate, propionate and citrate anions on the differential capacity vs.electrode potential curves of the Fe-HClO 4 system was examined. Each of these organic anions introduced a new adsorption-desorption peak, while both the water-reorientation peak and the ClO 4 − desorption peak were suppressed by the addition of the organic acids. The potential of the H-adsorption peak was shifted to more anodic values as a result of the adsorption of the negatively charged organic anions, but this peak was eventually suppressed as the concentration of the additives increased. Addition of ClO 4 − to the Fe-HClO 4 system containing acétate or propionate anions produced a broad peak. This is interpreted in terms of the co-adsorption of ClO 4 − and the organic anions. Such a peak was not appreciable in the case of citrate. The order of the degree of adsorbability of the organic anions, estimated from the extent of the suppression of C-E curves, was acetate < propionate < citrate.