Pseudokapacitivumas

Pseudokapacitivumas is a term used in electrochemistry to describe a phenomenon where a material exhibits capacitive behavior without a true charge separation mechanism, such as that found in conventional electrochemical capacitors (supercapacitors). Instead, this behavior arises from faradaic redox reactions that occur at or near the surface of the electrode material. These redox reactions involve the transfer of electrons and ions, leading to a change in the oxidation state of the electrode material.

Unlike true capacitive storage, where ions accumulate electrostatically at the electrode-electrolyte interface, pseudocapacitive storage involves a charge transfer process. This means that the process is not purely double-layer capacitance. The energy storage in pseudocapacitive materials is directly related to the number of redox-active sites available and the reversibility of the redox reactions. Materials commonly exhibiting pseudocapacitance include transition metal oxides (like RuO2, MnO2), conducting polymers (like polyaniline, polypyrrole), and some layered materials.

The key characteristic of pseudocapacitance is that the capacitance value is strongly dependent on potential and the kinetics of the redox reactions. This can lead to higher energy densities compared to pure double-layer capacitors, as more charge can be stored through these redox processes. However, the power density can be limited by the rate at which these faradaic reactions occur. Understanding and controlling pseudocapacitive effects is crucial for the design and optimization of energy storage devices, particularly batteries and hybrid supercapacitors.