Adsorption of n-Butanol from Aqueous Solutions on a Bi–Ga Electrode

Abstract

Curves of the differential capacitance at the Bi–Ga/H2O interface in 0.05 M Na2SO4 solutions with different concentrations of n-C4H9OH are obtained by a bridge method at 420 Hz and 32°C. Adsorption parameters of n-C4H9OH, determined by a regression analysis of these curves, are compared with relevant data for mercury and partially fused polycrystalline bismuth (pBi). That the adsorption behavior of organic molecules at Hg differs from that at pBi and Bi–Ga is due not to their different hydrophilicity but to a different physical interaction water–electrode. The reason for this phenomenon can be an unequal spread of electron density beyond the ionic cores of Hg and Bi. These notions are corroborated by the fact that the Bi–Ga data fit overall correlation dependence between the “electronic” capacitance of different electrodes in the absence of a chemisorption interaction metal–water and the adsorbability of the n-C4H9OH molecules on them.