Faradaic reactions’ mechanisms and parameters in charging of oils

Abstract

Leaky dielectric liquids, e.g. oils, constitute a class of conductors capable of being electrified to possess a net charge. Faradaic reactions have been recently demonstrated to be responsible for the electrification of such liquids as canola oil in electrostatic atomizers. Here we explain the fundamental chemical kinetics of the mechanisms responsible for charging of these oils at metallic electrodes and measure their parameters. Three main mechanisms of the electrode faradaic reactions of oil are recognized. (i) Cathodic reduction of protons resulting from fatty acid dissociation accompanied by anodic reactions with formation of metallo-organic deposits (metal salts of fatty acids). (ii) Redox reactions with participation of dissociated water molecules (the impurities) absorbed from the surrounding humidity. (iii) Redox reactions on a sharp pin electrode (either being a cathode or an anode) at higher voltages (with the magnitude above about 4 kV) leading to the Coulombic repulsion of charged oil from this electrode and the emergence of a toroidal vortex-like circulation in the oil bath. The electrochemical findings are corroborated by the results obtained by means of the Infrared spectroscopy and Raman spectroscopy of the electrode deposits, and the introduction of a novel method of measurement of the electric conductivity of oils used to establish the kinetic constants of the Frumkin-Butler-Volmer kinetics in the form of the Tafel plot.