Pseudokapacitás

Pseudokapacitás refers to a phenomenon observed in electrochemical systems, particularly in supercapacitors and batteries, where a material exhibits capacitive behavior that is not solely due to electrostatic charge storage (the true double-layer capacitance). Instead, this enhanced capacitance arises from fast, reversible faradaic redox reactions occurring at or near the electrode surface. These reactions involve the transfer of electrons between the electrode material and ions in the electrolyte, leading to charge storage through chemical changes.

Unlike ideal double-layer capacitors, which store charge by the accumulation of ions at the electrode-electrolyte interface without chemical transformation, pseudocapacitive materials undergo redox reactions. These reactions are typically much faster than those in bulk batteries, allowing for rapid charging and discharging, which is characteristic of supercapacitors. The pseudocapacitance contributes significantly to the overall energy density of these devices, often exceeding that of pure double-layer capacitance. Common materials exhibiting pseudocapacitance include metal oxides (like ruthenium oxide, manganese dioxide), conducting polymers (like polyaniline, polypyrrole), and some transition metal dichalcogenides. The magnitude of pseudocapacitance is dependent on factors such as the specific redox reactions involved, the electrode material's morphology and surface area, and the electrolyte composition. Understanding and controlling pseudocapacitance is crucial for developing high-performance electrochemical energy storage devices.