In some cases, the adsorbed molecule is chemically bonded to the surface/material, providing a strong adhesion and limiting desorption. If this is the case, desorption requires a chemical reaction which cleaves the chemical bonds. One way to accomplish this is to apply a voltage to the surface, resulting in either reduction or oxidation of the adsorbed molecule (depending on the bias and the adsorbed molecules).
In a typical example of reductive desorption, a self-assembled monolayers of alkyl thiols on a gold surface can be removed by applying a negative bias to the surface resulting in reduction of the sulfur head-group. The chemical reaction for this process would be:
where R is an alkyl chain (e.g. CH), S is the sulfur atom of the thiol group, Au is a gold surface atom and e is an electron supplied by an external voltage source.
Another application for reductive/oxidative desorption is to clean active carbon material through electrochemical regeneration.