On the behavior of CTAB/CTAOH adlayers on gold single crystal surfaces

The behavior of adsorbed CTAB and CTAOH on gold single crystal electrodes has been studied in solutions with different pH values. For the different single crystal electrodes, the adsorbed adlayer formed by CTA+ cations is in contact with the surface when the electrode charge is negative. As the surface charge becomes positive, the adlayer detaches from the surface and water molecules permeate through it, giving rise to characteristic peaks in the voltammogram. Charge and laser-induced jump temperature measurements show that the composition of the adlayer contains not only the CTA+ cations but also anions, which are required to stabilize the adlayer. In alkaline solutions, the higher solubility of CTAB/CTAOH in alkaline solutions leads to the partial desorption of the adlayer when these species are not present in the solution. When CTAB or CTAOH are dissolved in the alkaline cell solution, the adlayer is strongly bonded to the surface in the whole potential window due to the negative charge of the surface.