The Effect of Polarization Time and Experimental Conditions on EDL Formation at the Glassy Carbon Electrode and EMImBF₄ Interface

This study addresses the limited understanding of how time-dependent experimental factors affect electric double layer (EDL) stability and capacitance behavior in highly viscous ionic liquids (IL). The interface between the glassy carbon (GC) electrode and 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) was electrochemically characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods. The aim was to determine how different experimental protocols (number of cycles vs holding time, and EIS time delay period) influence the EDL formation in EMImBF₄ at a GC interface. The capacitance values have been shown to systematically depend on the polarization time and number of conducted EIS cycles. Furthermore, the influence of EIS time delay, i.e., the duration of applied fixed potential, was demonstrated. The results highlight the importance of standardizing the design and protocol of experiments to facilitate better comparability of collected experimental results. Results show that stable capacitance values can be achieved either through 14 days of resting times or within 8 h of continuous cycling, and that EIS time delay affects measured capacitance by up to 30%. This work contributes to a novel methodological control study in IL-based electrochemistry and has implications for applications such as supercapacitors and electrocatalytic interfaces, where precise EDL characterization is essential.