overpotential

Overpotential, also known as overvoltage, refers to the difference in potential required to drive an electrochemical reaction at a certain rate compared to the theoretical potential needed for that reaction to occur. This excess voltage is necessary because electrochemical reactions often involve multiple steps, and one step may have a larger energy barrier, slowing down the overall process.123

Electrocatalysis is the study of how to reduce this overpotential, thereby increasing the rate of electrochemical reactions. This is crucial for making electrochemical processes more economical and efficient, such as in fuel cells where chemical energy is converted into electrical energy. The Butler-Volmer equation quantitatively relates current density, electrode potentials, and overpotentials in electrochemical reactions.345