Development of a new modified carbon paste electrode by silver chloride: application to electrocatalytic oxidation of methanol

A new carbon paste electrode chemically modified with silver chloride is constructed. The silver chloride-modified carbon paste (SC-MCP) electrode was prepared by grinding the mixture of graphite powder and silicon oil (as a binder) with sufficient amount of silver chloride. Then, the electrode was placed in 0.1 mol L-1 NaOH and the electrode potential was cycled between 170 and 800 mV (vs. Ag/AgCl) at a scan rate of 50 mV s(-1) for 20 cycles in a cyclic voltammetry regime until a stable voltammogram was obtained. The electrocatalytic activity of the SC-MCP electrode was examined for the oxidation of methanol. In CV studies, no oxidation response of methanol can be seen at the unmodified electrode, indicating the nonelectro-activity of methanol on this substrate. But at the SC-MCP electrode, a large anodic peak appears at 757.4 mV, indicating that the anodic oxidation of methanol could be catalyzed at SC-MCP electrode. This proves that the silver chloride bears the main role in electrocatalytic oxidation of methanol. Kinetic parameters such as the electron transfer coefficient (alpha) and the number of electrons involved in the rate-determining step (n(alpha)) for the oxidation of methanol was determined utilizing cyclic voltammetry (CV). The modified electrode shows a stable and linear response in the concentration range of 5 x 10(-3)-6 x 10(-2) mol L-1 with a correlation coefficient of 0.9921.