Elektrodkapacitans

Elektrodkapacitans, in English electrode capacitance, is the ability of an electrode in an electrochemical cell to store electric charge. It is determined mainly by the electrical double layer that forms at the interface between the electrode surface and the surrounding electrolyte, but can also include contributions from fast surface redox reactions (pseudocapacitance) on certain materials.

The dominant component for most conventional electrodes is the electrochemical double layer capacitance. When a potential is applied, ions in the electrolyte rearrange near the electrode surface, creating a charge separation that behaves approximately like a capacitor. The double-layer capacitance is highly dependent on surface area, material, electrolyte composition, and temperature, and is typically on the order of tens of microfarads per square centimeter for common electrode–electrolyte systems. Some materials and electrolytes can increase this value, while rough or porous surfaces can effectively raise the active area and thus the total capacitance.

In some electrode materials, charge storage also occurs through rapid surface redox reactions, contributing pseudocapacitance. This can significantly enhance the overall electrode capacitance and energy storage, as seen in certain metal oxides and conducting polymers. The total electrode capacitance is then a combination of double-layer and pseudocapacitive contributions and may vary with potential.

Measurement and modeling of elektrodkapacitans are typically performed using electrochemical impedance spectroscopy or cyclic voltammetry. In circuit models, the electrode is represented by elements such as a resistance (solution resistance), a capacitor (double-layer), a charge-transfer resistance, and sometimes diffusion-related components. Understanding electrode capacitance is important for the design of energy storage devices, sensors, and corrosion studies.