The square wave voltammetry has advantages over other voltammetric techniques due to the resultant low current signal from the capacitive current while the difference of value between the sampling current of both the forward and reverse potential is higher than the absolute value of either sampling current. It additionally offers high speed and extended sensitivity in direction of electrode kinetic studies.
Cecilia Bonazzola and Gabriel Gordillo from University of Buenos Aires in Argentina provided a new methodology for electrode kinetic studies of surface reaction by altering either the amplitude, ESW, or the frequency, f, of the square wave potential perturbation.
Theoretical results show that the apparent standard rate constant, k0, the values of transfer coefficient α and number of exchanged electrons n affects the potential peak separation ΔEP and the ratio between the forward and reverse peak currents of the experimental square wave voltammogram. Moreover, the potential peak separation between the two peak currents is dependent on the dimensionless electrode kinetic parameter, k0/2f. The proposed function Ωn,α = ln(k0/2f) is also related to the peak separation due to known values of transfer coefficient and number of exchanged electrons.
When observing the dependence of function Ωn,α on the absolute value of potential peak separation, the degree of reversibility increased by frequency led to a linear dependence of the function Ωn,0.5 on the potential peak separation, However, the slopes of the function Ωn,0.5 versus the potential peak separation were found to be independent on the amplitude of the SWV experiment. At any amplitude, function Ωn,0.5 curves toward negative values when potential peak separation is lesser than 0.09/nV.
When authors looked at the dependence of corrected potential peak separation ΔEPC =2ESW –ïΔEPï. on amplitude for the same previous values of transfer coefficient and number of exchanged electrons showed two regions; the left side where corrected potential peak separation increases with amplitude known as the amplitude dependent region for potential peaks lesser than 0.090/nV and the right side where the corrected potential peak separation remained constant, known as the non-amplitude regions when observed for potential peak separation higher than 0.090/nV.
Known values of the number of exchanged electrons and transfer coefficient for the introduced function Ωn,α and the experimentals ΔEPC values, the standard surface rate constant is easily determined. Relative errors on the standard surface rate constant could also be determined.
The authors were also able to find good correlations between the calculated standard surface rate constant and the previous reported ones, which further proves that the methodology used in their research is very much applicable for electrode kinetic studies.
The analysis presented by the authors for studying electrode kinetic studies of surface reaction provides another alternative which would be relevant in the medical and sensing field.
Bonazzola, C., Gordillo, G. Advanced Analysis for Electrode Kinetic Studies of Surface Reactions by Applying Square-Wave Voltammetry, Electrochimica Acta 213 (2016) 613–619.Show Affiliations
- Ciclo Básico Común, Universidad de Buenos Aires, Buenos Aires, Argentina
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, AR-1428 Buenos Aires, Argentina
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