| Description |
Over the last two decades, boron-doped diamond electrodes (BDDEs) have begun to attract much attention in both basic and applied research. The originally non-conductive diamond can be used as an electrode material, as boron doping increases its conductivity. Particularly compared to traditional electrodes, BDDE is an outstanding durability electrode with unquestionable benefits, including uses in environmental monitoring, free chlorine biosensors, and wastewater treatment. These benefits are mostly explained by the boron element's doping, which contributes to the BDDE electrode's unique electrochemical characteristics. For example, a wide potential window in an aqueous solution, a very low background current, and different surface terminations can be used for different redox reactions. Combining theory (idea to eliminate one of the current components) and experiment (LSV or CV) resulted in elimination voltammetry with linear scan (EVLS), a useful method of further processing of voltammetric data. Eliminating a selected (specified) current using the elimination functions f(I) allows a better understanding of how changes in a single current can affect the overall electrochemical reaction. For example, both the diffusion current (Id) and the kinetic current (Ik) can be removed, conserving only the capacitive current. Capacitive current is closely connected with the charging of the electrode/electrolyte interface and therefore changes in the electric double layer are reflected by means of the elimination function preserving only the capacitive current component. We found that EVLS can effectively represent the change in the electrical double layer during the electrode reaction process. In the case of a reversible redox reaction with diffusion control and without kinetic complication, the simultaneous elimination of Id and Ik should provide the zero conserved charging current component (Ic); any deviation from the zero line indicates a complication. Such a deviation in the form of a depression was observed both on the anodic (oxidation of [Fe (CN)6]4-) and on the cathodic side (reduction of [Fe(CN)6]3-), and the double-sided record reminded the form of a drop. It should be noted that this effect is not limited to BDDEs, but has been observed on other graphite electrodes with different sizes and shapes. The EVLS approach to experimental data processing is revolutionary and distinctive. The following three EVLS functions with respect to the integer of 2 (I is the reference current, I1/2 and I2 are one-half and double of the reference current, respectively) were used. E4 f(I) = -11.6570I1/2 + 17.4850I - 5.8284I2, which eliminates simultaneously charging and kinetic currents while retaining the diffusion current, E5 f(I) = 6.8284I1/2 - 8.2426I + 2.4142I2, which eliminates simultaneously charging and diffusion currents while retaining the kinetic current, and E6 f(I) = 4.8284I1/2 - 8.2426I + 3.4142I2, which eliminate simultaneously the kinetic and diffusion currents while retaining the charging current. To confirm the superior performance of the BDDE electrodes, we first performed a short CV examination. It should be noted that these are screen-printed electrodes (i.e. SP-BDDEs) and SP-BDDEs surfaces were previously converted to the hydrogen termination by 5 mins polarization in 0.5 M H2SO4 at the potential -2 V. Using three scan rates, we performed EVLS diagnostics and found significant differences between the two methods of recording voltammetric recordings, when either a sample drop was applied to the SP-BDDE surface (drop mode - D) or the SP-BDDE was immersed in the sample solution (immersion mode - I). A big surprise for us was the differences in the values of charging and kinetic current components after EVLS procedures in both approaches. This contribution clearly demonstrates the importance of EVLS as an extension of voltammetric data processing methods that lead to deeper insight into electrode processes and their mechanisms.
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