Faradaic efficiency (${\eta }_F$)

Faradaic efficiency is the fraction of total transferred electric charge accounted for by a specified product. If production of one mole requires $z$ moles of electrons, then ${\eta }_F=zF{n}_{\mathrm{product}}/Q$, where $F$ is the Faraday constant and $Q$ is the measured charge.

For example, two-electron formation of one millimole of product accounts for approximately 193 coulombs. Dividing that charge by the total passed charge gives its Faradaic efficiency. The value differs from chemical yield, which compares product amount with a starting-material inventory.