The Butler-Volmer equation revisited: effect of metal work function

The Butler-Volmer equation is commonly the standard model of electrochemical kinetics.  Typically, the effects of applied voltage on the free energies of activation of the forward and backward reactions are analyzed and used to derive a current-voltage relationship. Traditionally, specific properties of the electrode metal were not considered in this derivation and consequently the resulting expression contained no information on the variation of exchange current density with electrode-material-specific parameters such as work function Φ. In recent papers^1,2, Buckley and Leddy revisited the classical derivation of the Butler-Volmer equation to include the effect of the electrode metal.  We considered in detail the complementary relationship of the chemical potential of electrons μ_e and the Galvani potential φ and so derived expressions for the current-voltage relationship and the exchange current density that include μ_e The exchange current density j₀ appears as an exponential function of Δμ_e.  Making the approximation Δμ_e ≈ —FΔΦ yields a linear relationship between ln j₀ and Φ. This linear increase in ln j₀ with Φ had long been reported³ but had not been explained.  In this webinar, these recent modifications of the Butler-Volmer equation and their consequences will be discussed.

¹ K S R Dadallagei, D L Parr IV, J R Coduto, A Lazicki, S DeBie, C D Haas and J Leddy,  J. Electrochem. Soc, 170, 086508 (2023)

² D N Buckley and J Leddy,  J. Electrochem. Soc, 171, 116503 (2024)

³ S Trasatti,  J. Electroanal. Chem., 39, 163—184 (1972)

D Noel Buckley is professor of physics emeritus at the University of Limerick, Ireland and adjunct professor of chemical and biomolecular engineering at Case Western Reserve University.   He is a fellow and past-president of ECS and has served as an editor of both the Journal of the Electrochemical Society and Electrochemical and Solid State Letters. He has over 50 years of research experience on a range of topics.  His PhD research on oxygen electrochemistry at University College Cork, Ireland was followed by postdoctoral research on high-temperature corrosion at the University of Pennsylvania.  From 1979 to 1996, he worked at Bell Laboratories (Murray Hill, NJ), initially on lithium batteries but principally on III-V semiconductors for electronics and photonics. His research at the University of Limerick has been on semiconductor electrochemistry, stress in electrodeposited nanofilms and electrochemical energy storage, principally vanadium flow batteries in collaboration with Bob Savinell’s group at Case. His recent interest in the theory of electron transfer kinetics arose from collaboration with Johna Leddy at the University of Iowa. He has taught courses in scientific writing since 2006 at the University of Limerick and short courses at several ECS Meetings. He is a recipient of the Heinz Gerischer Award and the ECS Electronics and Photonics Division Award. Recently, he led Poetry Evenings at ECS Meetings in Gothenburg and Montreal.