Fundamentals and implication of PZC determination for activated carbons in aqueous electrolytes

Abstract

The point of zero charge (PZC) is crucial for investigating molecular level charging mechanisms in energy storage systems, as demonstrated in electrochemical capacitors. Three electrochemical techniques were studied: cyclic voltammetry (CV), staircase potentio electrochemical impedance spectroscopy (SPEIS) and step potential electrochemical spectroscopy (SPECS) for two activated carbons (ACs) with 0.1 mol L− 1 aqueous solutions of LiNO3, Li2SO4, and KI. The porous AC charging process in aqueous electrolytes is a complex phenomenon; the ion mixing zone covered a wide potential region. Inadequate PZC determination could lead to obscure data evaluation, which could further provide a misguided mechanism description at the molecular level. In the aqueous solutions studied, the adsorption of specific ions and active participation of all ionic species in the electrical double-layer formation were considered. The SPECS technique was determined to be the most beneficial for the PZC determination in electrochemical quartz crystal microbalance applications.