ИСТИНА

By the impedance method (C,E- dependencies) we studied the adsorption of surfactants (camphor, sodium cryptate [Na+ Ì 2.2.2.] and 1-oxyadamantane (AdOH)) on electrodes modified with films of carbon nanowalls (CNWs), which represent a dense array of graphene-like sheets vertically oriented with respect to the conducting substrate (glassy carbon, nickel). Height and linear size of the CNWs are 1 µm and 0.5-1 µm, respectively. An area of the CNW film potential applications in both applied and fundamental fields can be far extended by their functionalization of both covalent and non-covalent nature. Moreover study of surfactant adsorption on such material is of great scientific interest. However, electrochemical and adsorption properties of this material are still not clearly understood. In the 0.1 M Na2SO4 solution with addition of camphor (8*10-3 M) jump-like increase in capacitance (up to 2.5 times) with its further insignificant variation in time is observed as compared with the maximum C in the supporting electrolyte. The increase in measured C can be associated only with increase in double layer electrode capacitance since cyclic voltammograms demonstrate absence of noticeable faradaic currents in the potential region under study, i.e., the faradaic capacitance contribution was virtually absent. The qualitatively analogous effects were observed in the presence of [Na+ Ì 2.2.2.] and AdOH and they were independent on the type of substrate. The experimentally observed increase in capacitance of the CNW electrodes at surfactant adsorption (despite the decrease in specific capacitance) may be explained by a predominance of effect of increase in the CNWs/electrolyte interface due to the partial «loosening» of the CNW film. Surfactants absorption on the CNW surface leads to their expansion due to Rehbinder effect. Consequently we actually observe the increase in material surface area accessible to the electrolyte leading to increase in double layer capacitance. According to our estimation, the CNW effective surface area increases up to 8—15 times due to adsorption. The revealed effect may be useful for thin film applications where graphene based materials are used.