koncentraatiopolaarisuuden

Koncentraatiopolaarisuus, sometimes translated as concentration polarization, is a phenomenon in electrochemistry and physical chemistry that occurs at the interface between an electrode and an electrolyte solution. It arises when the concentration of an electroactive species at the electrode surface deviates significantly from its concentration in the bulk solution. This deviation is typically caused by the rate of the electrochemical reaction being limited by the rate at which reactants can diffuse from the bulk solution to the electrode surface or by the rate at which products can diffuse away.

When an electrochemical reaction proceeds, the concentration of reactants near the electrode surface is depleted, and the concentration of products increases. If the rate of diffusion is not fast enough to replenish the reactants or remove the products, a concentration gradient is established. This gradient leads to a potential drop across the diffusion layer, which is known as concentration polarization. This polarization effect can significantly influence the overall current density and the observed electrode potential.

Concentration polarization is particularly noticeable at higher current densities, where the electrochemical reaction rate is high. It can be mitigated by factors such as stirring the electrolyte solution, which reduces the thickness of the diffusion layer, or by increasing the temperature, which enhances diffusion rates. Understanding and accounting for concentration polarization is crucial in various electrochemical applications, including batteries, fuel cells, and electroplating, as it directly impacts efficiency and performance. In some cases, concentration polarization can be the rate-limiting step for the entire electrochemical process.