(152d) Equilibrium and Rate Measurements with Potential-Sweep Voltammetry

Potential-sweep methods, of which linear-sweep voltammetry (LSV) and cyclic voltammetry (CV) are prime examples, can be used to quantify the equilibrium constants of electrochemical reactions, measure interfacial electron-transfer reaction rates, and determine the transport properties of electrolytes. This tutorial will discuss how using disk microelectrodes to implement LSV and CV can help to establish the rates and mechanisms of electrochemical reactions. We will briefly discuss the history of LSV and CV methods, give a set of primary references describing the techniques, and provide a more modern discussion based on currently popular reference texts [1–4]. 

The discussion will illustrate potential-sweep methods by example. We will focus on a reaction system from the redox-flow-battery literature, wherein an active species in the liquid phase can either oxidize or reduce. Depending on the voltage, the system can pass through three oxidation states. We will show how LSV and CV can be used to verify a hypothetical mechanism for this multi-step reaction, as well as showing how reactant transport properties can be deduced from the analysis of potential-sweep results.

References

1.  J.E.B. Randles, Trans. Faraday Soc. 44 (1948) 327.

2.  H. Matsuda and Y. Ayabe, Z. Electrochem. 59 (1955) 494.

3.  A. J. Bard and L. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2^nd Edition, (New York: Wiley, 2001).

4.  J. Newman and K. Thomas-Alyea, Electrochemical Systems, 3^rd Edition, (New York: Wiley, 2004).