EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium

TL;DR

This paper introduces EC-FORC, a cyclic voltammetry technique that distinguishes phase transition types and accurately predicts equilibrium states, enabling rapid in-situ electrochemical analysis.

Contribution

The paper presents a novel EC-FORC method that differentiates phase transition types and recovers equilibrium behavior from dynamic voltammetry data.

Findings

EC-FORC diagrams show negative regions for discontinuous transitions.

Minima of EC-FORCs trace equilibrium curves at high scan rates.

Method can be implemented with simple reprogramming of existing equipment.

Abstract

We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The Electrochemical first-order reversal curve (EC-FORC) diagram for a discontinuous phase transition (nucleation and growth), such as occurs in underpotential deposition, is characterized by a negative region, while such a region does not exist for a continuous phase transition, such as occurs in the electrosorption of Br on Ag(100). Moreover, for systems with a continuous phase transition, the minima of the individual EC-FORCs trace the equilibrium curve, even at very high scan rates. Since obtaining experimental data for the EC-FORC method would require only a simple reprogramming of the potentiostat used in conventional cyclic-voltammetry experiments, we believe that this method has significant potential for easy, rapid, in-situ analysis of systems undergoing electrochemical deposition.