Résumé
In this work, we aim to explore the synergetic influence of the functionalization of the carbon electrode and that of the electrolyte pH on the charge storage mechanism by utilizing the technique of EQCM (Electrochemical Quartz Crystal Microbalance). A comparative analysis has been carried out on YP50 and o-YP50 (carbon with oxygen functionalities), which revealed crucial differences in the evolution of ionic contribution to charge storage under varying pH. A progression from anionic to cationic mechanism was observed with an increase in pH, depending on the isoelectric point of the carbon under study. A combination of TPD-MS (Temperature Programmed Desorption Mass Spectrometry) and EQCM was used to probe pH-dependent surface transformations occurring on the functionalized and non-functionalized carbon electrode during electrochemical cycling. The electrolyte pH governs the protonation state of the surface functional groups, which influences the charge on the electrode and hence the mechanism of charge storage.