Carbon Dioxide Sensor Consisting of K 2 CO 3 ‐ Polyethylene Glycol Solution Supported on Porous Ceramics: II . Study of Mechanism by Employing Cyclic Voltammetry
Cyclic voltammograms of the solution have been investigated as a function of the working electrode materials as well as concentration of in gas mixtures which were blown through the solution prior to the measurement. The current‐potential curves on the negative scan obtained with the Au or Ag electrode were more sensitive to the concentration change of in the flowing mixture than those obtained with the Pt or Pd electrode. Further experiments with the Au electrode have revealed that there were two different potential regions in which the currents markedly varied with the concentration of in mixtures: −0.5 to −1.3V and more negative than −1.3V vs. SCE. In the former range, between −0.5 and −1.3V, the currents at constant potentials decreased as the concentration of increased. This behavior was suggested to be caused mainly by the substitution of for dissolved in the solution. At potentials more negative than −1.3V, on the other hand, the currents increased as the concentration of increased, suggesting that some electrochemical reduction of the dissolved was occurring. From these results, possible mechanisms of the sensor element consisting of solution supported on porous ceramics have been discussed.