INFLUENCE OF FREQUENCY OF ELECTRIC CURRENT ON ELECTRIC CONDUCTIVITY OF THIN FILMS OF ELECTROLYTES
Authors: Nefedov Vladimir G. , Matveev Vadim V. , Korolyanchuk Dmytriy G. 
Published: January 2018

In the work the investigations of the effect of abnormally high electric conductivity of surface of the air-electrolyte interface during electrolytic decomposition of water were continued. Experiments were carried out both at alternating current via the bridge circuit and at direct current in the four-electrode cell. Previously, it was shown that in thin air-bordering electrolyte layers specific conductivity measured in the four-electrode cell during electrolysis of water exceeds the corresponding value measured with the bridge circuit for solutions of sodium hydroxide by 1.5 times, for solutions of sulfuric acid by 1.25 times and for solutions of sodium sulfate by 2.5 times. When replacing the gas-liquid interface by the liquid-solid phase one the effect disappears. It was shown that the abnormally high electric conductivity of thin air-bordering electrolyte layers depends on temperature (at 4 °С electric conductivity of 1 mm thick solution layer increases 8-12 times), ion composition, pH (maximum 5 times increase of electric conductivity corresponds to pH of isoelectric point). This allowed suggesting that such effect is caused by tunneling of charge (without mass transfer) through ordered structures on the surface of water - giant heterophase clusters. This mechanism has been called croquet. To check the influence of surface the experiments in 1 mm and 0.1 mm thick layers of electrolyte were conducted. Thin electrolyte films were stabilized by the DC-10 surfactant and the thickness was measured by interferometric methods. It has been shown that specific electric conductivity of thin films increases by 150-250 times in comparison with conductivity of the original electrolyte. This confirmed our assumptions on the nature of the effect of abnormally high electric conductivity of the gas-electrolyte interface during electrochemical generation of uncompensated H+ and/or OH- ions. Surprisingly, it appears that specific electric conductivity of the electrolyte film of thickness below 50 μm as measured at the 10 kHz alternating current is also higher than conductivity measured with the same method in the initial electrolyte volume. The values of electric conductivity of thin electrolyte films measured by different methods were almost identical. It has been suggested that this phenomenon is related to the changed conditions of charging of the double electric layer. To test the hypothesis, the values of specific electric conductivity of 1 mm thick electrolyte layer were measured at changing from 10 kHz to 0.1 Hz frequencies of alternating current. It was shown that the effect of increase in the electric conductivity begins to occur at frequencies up to 1 kHz. Calculations showed that at these frequencies the quantity of electricity transferred to the electrodes is sufficient for charging the double layer and initiation of the Faraday process. Thus, another confirmation that the croquet mechanism of electric conductivity occurs at the two conditions – the electrolytic generation of H+ or OH- ions and the transfer of charges through ordered structures on the surface of water – was found.Forcitation:Nefedov V.G., Matveev V.V., Korolyanchuk D.G. Influence of frequency of electric current on electric conductivity of thin films of electrolytes. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 58-64