Alternative method to obtain the Tafel plot for simple electrode reactions using batch injection analysis coupled with multiple-pulse amperometric detection

Abstract

The application of the batch injection analysis coupled with multiple-pulse amperometric (BIA-MPA) detection is proposed as an alternative method to obtain the kinetic parameters for simple redox reactions (e.g., Fe(CN)63−/4−, Ru(NH3)3+/2+ and Fe(H2O)63+/2+) from analysis of the Tafel plot (TP). The kinetic studies were performed to permit the ‘in situ’ surface characterisation of thin, boron-doped diamond (BDD) films that exhibit a high conductivity. The evaluation of the apparent equilibrium electrode potential (Eeq) and the kinetic parameters comprising the exchange current (i0), the anodic and cathodic charge-transfer coefficients (αa and αc), as well as the apparent heterogeneous rate constant (ko), were evaluated through the analysis of the Tafel plots. According to the experimental values of ko, the degree of reversibility strongly depends on the particular redox reaction occurring on the surface of BDD. The ko values obtained for the different redox reactions from analysis of the Tafel plot were compared with those obtained using the electrochemical impedance spectroscopy (EIS) technique. A good agreement for the kinetic parameters determined for the different redox reactions using different experimental approaches (TP and EIS) was obtained through the statistical analysis based on the standard deviation obtained for the different ko values, after five different measurements for each redox reaction. The use of the proposed alternative method for the study of simple electrode reactions can be very helpful because these reactions are often used as a ‘probe’ for the ‘in situ’ surface characterisation of new electrode materials developed for different purposes.