Derivative-Extremum Analysis Principle for Irreversible Electrode Reactions: Feature Parameter Extractions from Polarization Curves
2019
Yin, Fengjun | Liu, Yuan | Liu, Hong
To ascertain the kinetic information of an irreversible electrode reaction, we extract two parameters of half-wave potential (E₁/₂) and peak value (PV) from the polarization curve through a derivative-extremum analysis. The E₁/₂ and PV are demonstrated to be two feature parameters corresponding to a special kinetic state, with electron transfer and reactant mass transport reaching a balance. This definition covers the characteristics of the inflection point in the polarization curve and the peak point in the derivative curve. A set of equations centering on E₁/₂ and PV are derived serving to disclose their significances in irreversible case and are verified by oxalic acid oxidation, nitrite oxidation, and oxygen reduction reaction. It is clarified that the E₁/₂ in the irreversible case is dominated by the standard potential and standard rate constant and characterizes the potential feature. Meanwhile, PV is an activation feature parameter associated with the activation rate driven by overpotential. Thus, a derivative-extremum analysis principle toward irreversible reactions is formed, providing an electrochemical insight for understanding the half-wave potential and enabling quantitative investigation of kinetic features and convenient parameter estimations in the irreversible electrochemical matrix.
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