Visualization of Chlorine Evolution at Dimensionally Stable Anodes by Means of Scanning Electrochemical Microscopy

摘要

Scanning electrochemical microscopy (SECM) has been used to detect and visualize the local electrocatalytic activity of dimensionally stable anodes (DSA) for Cl_(2) evolution from brine. The sample generation-tip collection (SG-TC) mode of SECM shows limitations arising from complications connected with the reduction of Cl_(2) at the SECM tip due to the presence of a significant amount of nondissolved Cl_(2) gas. Because only dissolved Cl_(2) can be electrochemically reduced at the tip, a large amount of the Cl_(2) gas which is produced at active spots of the DSA is not detected. Additionally, a decrease of the cathodic current at the tip may occur owing to the adhesion of gas bubbles and blocking of the electrode surface. To overcome this limitation, the redox competition mode of SECM was extended and applied to the local visualization of Cl_(2) evolution from highly concentrated brine solutions. High concentrations of Cl_(2) produced at the sample can cause inhibition of the same reaction at the tip by accumulation of Cl_(2) in the proximity of the SECM tip. In this way the tip current is decreased, which can be used as a measure for the catalytic activity of the sample underneath the tip.