Why do different electrode materials change the speed of electrochemical reactions?

In electrochemical reactions, the electrode acts as a substrate that can significantly influence reaction rates, a field of study known as electrocatalysis.

While simple electron transfer processes are generally independent of the metal substrate, reactions that involve the formation of chemical bonds between the electrode surface and intermediate species are highly sensitive to the material used. The speed of these reactions varies based on the strength of the bond established between the surface and the intermediate particles.1

The relationship between the electrode material and the reaction rate follows these principles:

• Bond Strength: If the bond between the surface and the intermediate species is too weak, the catalytic effect is minimal. If the bond is too strong, the intermediate becomes too stable to react further, effectively blocking the surface.1
• Optimum Efficiency: There is an optimum bond strength for any given reaction. This is often observed when plotting the reaction rate against a property of the metal substrate proportional to its ability to form bonds, such as its heat of sublimation.1
• Surface Interference: The presence of foreign species, such as organic molecules, can inhibit reactions by blocking the electrode surface, while specific ions can alter the reaction rate by modifying the properties of the electric double layer.12