Reply to comments on Intrinsic limitations of impedance measurements in determining electric double layer capacitances by H. Wang, L. Pilon [Electrochimica Acta 63 (2012) 55]

In the commentary to our paper [Electrochimica Acta 63 (2012) SS], Roling and Druschler raised a very important issue regarding the measurements and comparison of the differential and integral capacitances retrieved using electrochemical impedance spectroscopy (EIS). They clearly explained that EIS measures differential capacitance rather than integral capacitance. The present letter aims to correct our previous study. It also clarifies the fact that cyclic voltammetry (CV) and galvanostatic methods can measure both differential and integral capacitances. Similar confusion exists in the literature on electrical energy storage devices and may explain discrepancies reported when measuring the capacitances of supercapacitors using EIS, CV, or galvanostatic methods. Finally, our original paper, for the first time, solved a modified Poisson-Nernst-Planck model with a Stern layer for simulating EIS. It also presented an interpretation of capacitance dispersion and a scaling analysis of electric double layers in EIS simulations. The model, scaling analysis, and the associated results were not affected by the confusion pointed out by Roling and Druschler. (C) 2012 Elsevier Ltd. All rights reserved.