Probing the Influence of Isoelectric Point-on-Charge Storage Mechanisms in Carbon Materials Using Electrochemical Quartz Crystal Microbalance (EQCM)

To overcome the global energy crisis driven by the depletion of fossil fuels and to address the increasing concerns around a cleaner and sustainable energy future, it is necessary to develop energy storage systems with high electrochemical performance. In this context, two complementary strategies are extensively explored: energy-dense batteries and high-power supercapacitors.

For carbon-based systems, coupling the electrochemical double-layer electrostatic storage with a high-rate redox (faradaic) contribution through the addition of small redox molecules constitutes an attractive approach to increase the charge storage capability of supercapacitors. The introduction of redox-active oxygen-containing functional groups (OFGs) in carbon improves the wettability of their surface and also increases their specific capacitance, and hence stands out as an attractive optimization strategy.

Recent research has shed light on the critical role of pH in determining the charge storage mechanism and overall electrochemical performance of carbon-based supercapacitors. In this work, the surface functional groups on the synthesized carbon material were analyzed using EQCM (Electrochemical Quartz Crystal Microbalance) to give an insight into the influence of pH on the charge storage mechanisms of the carbon in aqueous electrolytes. Comparative studies performed on the non-oxidized and oxidized carbon further support the significant improvement in electrochemical performance observed in the latter. This study lays the foundation for future modifications in carbon materials and optimizing the electrolyte pH to improve supercapacitor performance.