ELECTROCHEMICAL PRETREATMENT OF CARBON ELECTRODES AS A FUNCTION OF POTENTIAL, PH, AND TIME

The electrochemical pretreatment of carbon electrodes through the oxidation and reduction of the electrode surface is a widely used procedure to improve electrode response; however, there still remain many unanswered questions about the nature of the pretreatment process. The main variables of the pretreatment process are the oxidation and reduction potentials, the composition and pH of the electrolyte solution, and the length of time of oxidation and reduction, This study focuses on the effects of these variables on the primary redox reactions that are responsible for activation of the electrodes. In the first part of this study, an anodic process starting at +1.6 V (SCE) and a cathodic process with a peak potential of approximately -1.0 V were observed with a glassy carbon electrode in solutions of pH 12 or greater, These processes are similar to those reported for pretreatment in acidic and neutral solutions and are distinct from the previously reported anodic process in 1 M NaOH which occurs between +0.9 and +1.5 V and gives a cathodic process with a peak potential at +0.2 V, In the second part of this study, the pH dependence of the anodic and cathodic processes in the pH range from 2 to 12 was examined by changing the pH of the solution during the course of oxidizing and reducing a glassy carbon electrode surface while keeping the electrode under potential control at ah times. The results support the idea of the formation of different species on the electrode surface when anodization is done at different pH's, During the course of the study, the length of time of anodization also was found to have an effect on the observed reduction potentials.