Electrochemistry in Near-Critical and Supercritical Fluids. 2. Water. Experimental Techniques and the Copper (II) System

摘要

An electrochemical cell and electrode system for investigation of aqueous systems under near- and supercritical conditions is described. Cyclic voltammetry of 1.5% w.w. KCl and 6% w.w. KBr solutions were investigated and log current vs potential (Tafel) plots for the chlorine and hydrogen evolution reactions are given. A study of the Cu/Cu(I)/Cu(II) system in Sodium Sulfate and Potassium Chloride solutions is described and the variation of the standard potentials of the half-reactions with temperature (to ca. 300 C) is given. The diffusion coefficient for Cu(II) was determined by chronoamperometry as a function of temperature (22-245 C) and shown to increase from .0000054 cc/s at 22 C to .0003 cc/s at 245 C. The change of diffusion coefficient with temperature was larger than that predicted by the Stokes-Einstein equation at temperatures above 175 C. Reprints.