Levich Analysis and the Apparent Potential Dependency of the Levich B Factor

Levich analysis is a frequently used method for extraction of diffusional properties of electrochemical active species. The analysis is based on plotting current versus the square root of the rotation rate of a rotating disc electrode. From the slope of this plot, the Levich B factor and the diffusional parameters may be obtained. In this article, we focus on issues related to the extraction of the B factor from experimental measurements. We show that the plot does not fully linearize the data: a prerequisite for the slope extraction. Furthermore, analyzing data at various potentials results in varying values of the B factor, contrary to predictions by theory. Thus, as an alternative, we introduce a omega(1/2)-normalized Levich plot. This plot linearized the data and the resulting B factor was potential-independent. The difference between the two methods is ascribed to the consideration that the electrolyte-electrode interface current may be limited. We conclude that the potential-dependent B factor based on the standard Levich analysis is an artifact and the resulting values are systematically underestimated in comparison to results from the omega(1/2)-normalized Levich analysis.