Metals {electrode}| can contact solutions. Corrosion, electrolysis, electroplating, and batteries involve electrodes.
oxidation
At anode, ions enter solution, so anode is negative, and solution is positive. Oxidation is at anode surface, and reduction is at cathode surface. Opposite charges surround electrode charges, and solution ions solvate, with high attraction at surfaces. Charge gradient is higher for higher concentration and higher ion mobility. Higher temperature reduces attraction, by breaking up surface layer. Applied electric force reduces attraction.
current
Ion formation or discharge rate is current density, which is 0 at equilibrium. Ion far from electrode feels net force. At 10^-7 meters, ion sees widely distributed charges, as it enters ion layer around electrode and feels constant voltage. When ion reaches electrode surface, voltage changes rapidly to opposite sign. Finally, ion reaches electrode pure metal.
At high current, potential can be constant, such as at hydrogen electrode or calomel electrode. If high overvoltage causes high current density, diffusion can be too slow, and electrode can become polarized. Adding extra potential or moving electrodes reduces polarization. Solution friction causes slower cation flow than electron flow, causes ohmic resistance, and decreases current. Power generation maximizes if concentration polarization is just below limiting current.
Physical Sciences>Chemistry>Analytical Chemistry>Electricity>Electrode
5-Chemistry-Analytical Chemistry-Electricity-Electrode
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0224