Online monitoring of electrochemical synthesis of 4-nitrocatechol using fast Fourier transform continuous cyclic voltammetry (FFTCCV) in flow system

This work describes the application of a new electrochemical technique for online monitoring of electrosynthesis using fast Fourier transform continuous cyclic voltammetry (FFTCCV). The electrochemical system included two compartments, a batch electrosynthesis cell and a flow analysis system. In the electrosynthesis cell, the formation of 4-nitrocatechol (4NC) took place via reaction of o-benzoquinone (o-BQ) with nitrite ion. In the flow cell, FFTCCV was used for monitoring the concentration of catechol at a gold ultramicroelectrode. Each measurement was done at the potential range −1.00-0.40 V at a scan rate of 10 V/s for 8000 s, in which the electrode signal was calculated by integrating the current in the selected potential range. Also, using FFTCCV technique, an intermediate was detected and used to find the mechanism of the electrochemical reaction. The redox peak of 4NBQ to 4NC was observed at +0.27 V, whereas the peaks of 4-nitrosocatechol (4NSC) and the intermediate were detected at −0.39 V. The results showed that the used electrochemical system is very useful for online monitoring and investigation of fast electrochemical reactions.