Point of Zero Charge - Application in Electrochemistry

Application in Electrochemistry

In electrochemistry, the electrode-electrolyte interface is generally charged. If the electrode is polarizable, then its surface charge depends on the electrode potential.

IUPAC defines the potential at the point of zero charge as the potential of an electrode (against a defined reference electrode) at which one of the charges defined is zero.

The potential of zero charge is used for determination of the absolute electrode potential in a given electrolyte.

IUPAC also defines the potential difference with respect to the potential of zero charge as:

E_pzc = E - E_σ=0

where:

• E_pzc - the electrode potential difference with respect to the point of zero charge,E_σ=0
• E - the potential of the same electrode against a defined reference electrode, V
• E_σ=0 - the potential of the same electrode when the surface charge is zero, in the absence of specific adsorption other than that of the solvent, against the reference electrode as used above, V

The structure of electrolyte at the electrode surface can also depend on the surface charge, with a change around the pzc potential. For example, on a platinum electrode, water molecules have been reported to be weakly hydrogen-bonded with "oxygen-up" orientation on negatively-charged surfaces, and strongly hydrogen-bonded with nearly flat orientation at positively charged surfaces.