Definition - What does Current Efficiency mean?
Current efficiency is the ratio of the actual mass of a substance liberated from an electrolyte by the passage of current to the theoretical mass liberated according to Faraday's law. Current efficiency can be used in measuring electrodeposition thickness on materials in electrolysis.
Current efficiency is also known as faradaic efficiency, faradaic yield and coulombic efficiency.
Corrosionpedia explains Current Efficiency
Current efficiency is the ratio of the electrochemical equivalent current density for a specific reaction to the total applied current density. Current efficiency describes the efficiency with which charge (electrons) is transferred in a system facilitating an electrochemical reaction. This phenomenon was originally understood through Michael Faraday's work and expressed in his laws of electrolysis.
In mathematical terms:
- m = (M×I×T) / (N×F)
- m = Theoretical yield (current efficiency)
M = Molar mass (weight of displaced element in grams)
I = Amperes
T = Time in seconds
N = Oxidation state (number of displaceable electrons per atom)
F = Faraday's constant (96487 Coulombs)
For example, the current efficiency in copper powder electrodeposition is a very important parameter from the energetic point of view, as well as from the point of view of the powder deposition rate. In general, it is known that the current efficiency in copper electrodeposition decreases with increasing deposition current density, concentration of sulphuric acid and increases with increasing copper concentration, electrolyte solution flow rate and temperature.
Under normal electroplating conditions, the quantity of metal deposited at the cathode or dissolved at the anode can be measured from current efficiency. Cathode efficiency is current efficiency as applied to the cathode reaction, and anode efficiency is current efficiency as applied to the anode reaction.
The ratio of the weight of metal actually deposited to that which would have resulted if all the current had been used for deposition is called the cathode current efficiency with respect to metal deposition.