APPLICATION OF LINEAR ROTATION-SCAN RRDE THEORY IN ELECTROCHEMICAL MEASUREMENT

A linear rotation-scan rde and rrde theory was derived and investigated for the electrochemical reduction of K3Fe(CN)6 and the electrochemical oxidation of ascorbic acid. The rate constant of ascorbic oxidation of PG electrode in pH 7.2 buffer solution was measured using the linear rotation-scan method. If the activity of electrode is quite stable, the i-ω curves obtained from the linear rotation-scan (whose current deviation has been corrected by a method of plotting) cannot vary with the rotation-scan rate of electrode (10 s-1000 rpm s-1), and the forward and backward scans are repeated. If the electrode activity is not stable enough, the current in the higher ω value part of i-ω curve will change to a lower value than the normal, leading to a separation between the forward and backward scans with decreasing rotation-scan rate of electrode. Because it has the property of rapidity, accuracy and high reproducibility, the rotation-scan method is applicable especially to studying electrochemical systems that are not sufficiently stable. A comparison between i-ω and i-E data shows that the i value of i-E data nearby E 1 2 deviates to a higher value than that of i-ω data, but the value at other potentials is nearly the same for both of them. © 1990.