Charge effects on the behavior of CTAB adsorbed on Au(111) electrodes in aqueous solutions

Spectroelectrochemical Studies of CTAB Adsorbed on Gold Surfaces in Perchloric Acid

“…However, the general trend of the ν­(CH) and δ­(CH 2 ) bands is easily seen when cycles are long enough for the adsorption layers to rearrange, as seen in Figure which shows a series of spectra over a complete cycle after 100 cycles. Here, the growth of the δ­(CH 2 ) bands is seen to follow the same behavior of the ν­(CH) bands, but in the opposite direction, a tendency that occurs when CTAB is adsorbed on Au(111) . This suggests that the adlayer reorientated when it detached from the surface and precipitated into CTAClO 4 .…”

“…Interestingly, the voltammetric profile obtained in the potential region below 1.2 V after oxidising the surface by extending the positive potential limit to 1.7 V is essentially identical to the stationary profile obtained by continuously cycling up to 1.2 V (Figure 2B). As demonstrated for single crystal electrodes, 20 this behaviour can be explained by the formation of a stable CTA + layer after expelling the Br − anions. At sufficiently negative potentials, the negative charge on the electrode surface maintains the adlayer attached to it.…”

“…Nevertheless, Br – is electrostatically repelled from the surface and replaced by ClO 4 – during the continuous cycles due to absence of bromide in the supporting electrolyte (which creates a concentration gradient that drives bromide away from the surface). This process can be accelerated at low potentials, where the charge of the surface is negative, and anions are repelled by the negative surface charge . Thus, it can be proposed that initially CTAB adsorbs forming micelles on the surface, which open in the presence of perchlorate to form a stable adlayer as bromide anions are progressively displaced by perchlorate.…”

“…Based on all this, the adsorption behaviour of CTA + has been studied on gold single-crystal electrodes, particularly on Au(111), Au(100), and Au(110). , CTAB adsorbs spontaneously on gold surfaces. Upon cycling, bromide desorbs leading to the formation of CTA + in perchloric acid solutions . Furthermore, CTA + experiences an attachment/detachment process modulated by the charge density on the electrode surface.…”

“…Upon cycling, bromide desorbs leading to the formation of CTA + in perchloric acid solutions. 20 Furthermore, CTA + experiences an attachment/detachment process modulated by the charge density on the electrode surface. As the head of CTA + is positively charged, the molecule is electrostatically repelled from the surface at potentials more positive than the pzc, without being diluted into the bulk of the solution, and re-attaches back to the surface if the charge density is made negative again.…”