The analyte has to be redox active within the potential window to be scanned. The utility of cyclic voltammetry is highly dependent on the analyte being studied. In this situation, the CV experiment only samples a small portion of the solution, i.e., the diffusion layer at the electrode surface. This relationship is described by the Randles–Sevcik equation. Hence, CV data can provide information about redox potentials and electrochemical reaction rates.įor instance, if the electron transfer at the working electrode surface is fast and the current is limited by the diffusion of analyte species to the electrode surface, then the peak current will be proportional to the square root of the scan rate. The more reversible the redox couple is, the more similar the oxidation peak will be in shape to the reduction peak.
If the redox couple is reversible, then during the reverse scan (from t 1 to t 2), the reduced analyte will start to be re-oxidized, giving rise to a current of reverse polarity (anodic current) to before. At some point after the reduction potential of the analyte is reached, the cathodic current will decrease as the concentration of reducible analyte is depleted. In Figure 2, during the initial forward scan (from t 0 to t 1) an increasingly reducing potential is applied thus the cathodic current will, at least initially, increase over this time period, assuming that there are reducible analytes in the system. These data are plotted as current ( i) versus applied potential ( E, often referred to as just 'potential'). The potential is measured between the working electrode and the reference electrode, while the current is measured between the working electrode and the counter electrode. The rate of voltage change over time during each of these phases is known as the experiment's scan rate (V/s). In cyclic voltammetry (CV), the electrode potential ramps linearly versus time in cyclical phases (Figure 2).
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