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In other words, the exchange current density is the rate of reaction at the reversible potential (when the overpotential is zero by definition). At the reversible potential, the reaction is in equilibrium meaning that the forward and reverse reactions progress at the same rates. This rate is the exchange current density.
The electrode potential may be either that at equilibrium at the working electrode ("reversible potential"), or a potential with a non-zero net reaction on the working electrode but zero net current ("corrosion potential", "mixed potential"), or a potential with a non-zero net current on the working electrode (like in galvanic corrosion or ...
The equilibrium potential for an ion is the membrane potential at which there is no net movement of the ion. [1] [2] [3] The flow of any inorganic ion, such as Na + or K +, through an ion channel (since membranes are normally impermeable to ions) is driven by the electrochemical gradient for that ion.
In electrochemistry, the Nernst equation is a chemical thermodynamical relationship that permits the calculation of the reduction potential of a reaction (half-cell or full cell reaction) from the standard electrode potential, absolute temperature, the number of electrons involved in the redox reaction, and activities (often approximated by concentrations) of the chemical species undergoing ...
The reversal potential (or equilibrium potential) of an ion is the value of transmembrane voltage at which diffusive and electrical forces counterbalance, so that there is no net ion flow across the membrane. This means that the transmembrane voltage exactly opposes the force of diffusion of the ion, such that the net current of the ion across ...
[1] [2] At chemical equilibrium or in phase equilibrium, the total sum of the product of chemical potentials and stoichiometric coefficients is zero, as the free energy is at a minimum. [3] [4] [5] In a system in diffusion equilibrium, the chemical potential of any chemical species is uniformly the same everywhere throughout the system. [6]
Just as in mechanics, the system will tend towards a lower value of a potential and at equilibrium, under these constraints, the potential will take the unchanging minimum value. The thermodynamic potentials can also be used to estimate the total amount of energy available from a thermodynamic system under the appropriate constraint.
This is represented by the green curve in the above figure. The equilibrium rate constants will be written as k fe and k be, and the equilibrium concentrations will be written c oe and c re. The equilibrium currents (j ce and j ae) will be equal and are written as j o, which is known as the exchange current density.