ChemInform Abstract: Specific Features of the Kinetics of Gas‐Evolving Reactions on Highly Active Electrodes

Abstract

Abstract The equations of the steady-state polarization curve and the potential decay curve (pdc) upon current interruption were analysed for the electrochemical gas-evolving processes on the electrodes with high electrocatalytic activity under conditions when removal of reaction product is the rate-determining step of the overall process. It is shown that the criteria of the high electrocatalytic activity of these electrodes are the existence, on the polarization curve, of a Tafel section with “Nernstian” slope, 2.3 R T/nF, its position depending on the solution stirring intensity, at low and medium current densities; and a low polarizability section at high current densities under intensive gas evolution, as well as the existence, on pdc, of an almost horizontal section determined by gradual change of the equilibrium open circuit electrode potential in time, as a result slow removal of reaction product from the near-electrode layer supersaturated with it. The above criteria were applied for kinetics analysis of the process of chlorine anodic evolution from acidified concentrated chloride solutions at high temperature (under chloralkali electrolysis conditions). It is shown that ruthenium based dimensionally stable anodes (DSA), as well as the smooth platinum anode activated by cyclic anodic—cathodic treatment, have very high electrocatalytic activity with respect to the chlorine evolution process.