Direct separation of faradaic and double layer charging current in potential step voltammetry

Double layer charging current in electrochemical systems has been a challenging problem in the last several decades because it causes interference to the accurate measurement of faradaic current. A method for extracting faradaic current and double layer charging current directly from the measured total current in potential step voltammetry is developed by using iterative target transformation factor analysis (ITTFA). The method constructs initial target vectors based on the theoretical formulae of faradaic and charging current, and then calculates the weights of faradaic and charging current in the measured signal via the iterative transformation of the initial vectors. Therefore, the two currents in one experiment can be obtained simultaneously without any assumption. The potential step voltammetric signals of potassium ferricyanide, copper sulfate and paracetamol were analyzed with the proposed method. The results show that the shape of the obtained voltammogram is an ideal sigmoid curve with horizontal straight baseline and plateaus, and the intensity of the signal is greatly enhanced. Therefore, the method provides a new way to measure the pure faradic current in the potential step voltammetric experiment, and may provide an alternative for improving the sensitivity of quantitative analysis.